KR100400522B1 - Electrolytic phosphating process and composite coating formed on steel surface - Google Patents

Abstract

The present invention provides a phosphate chemical treatment technique suitable for electrolytic treatment.

In the present invention, at least phosphate ions and phosphoric acid, nitrate ions, metal ions forming complexes with phosphate ions in the phosphate chemical treatment bath, and ions dissolved in the phosphate chemical treatment bath are reduced and precipitated as metals. Disclosed is a phosphate chemical treatment bath containing a metal ion above the nodal electrolysis potential.

The concentration of metal ions other than the coating component in the treatment bath is 0 to 400 ppm, and the treatment bath is substantially free of solids that affect the coating formation reaction.

Description

ELEPHTROLYTIC PHOSPHATING PROCESS AND COMPOSITE COATING FORMED ON STEEL SURFACE}

Japanese Patent No. 5-822481 discloses an electrolytic treatment using a phosphate chemical treatment bath that is essentially free of sludge and contains nitrogen-containing oxo acid ions, phosphate ions, and film component metal ions. . This treatment bath is characterized in that it does not generate sludge at pH 2 to 4 and at a temperature of 40 ° C. or lower.

However, since the phosphate chemical treatment bath disclosed in Japanese Patent No. 5-822481 described above uses sodium hydroxide to adjust the pH, or because sodium nitrite is used as an accelerator irrelevant to the coating component, It cannot be called an electrolytic phosphate chemical treatment method for forming a silver film efficiently.

Accordingly, in view of the above problems, the present invention provides a phosphate chemical treatment method capable of forming the film efficiently and the composite film obtained by the method.

Prior to describing the electrolytic phosphate chemical treatment method of the present invention, the difference between the "electrolytic treatment" and "electroless treatment" surface treatment techniques using an aqueous solution will be described first.

This distinction is evident when we talk about "plating," a widely used wet surface treatment technique.

That is, there are two types of plating, an "electrolytic method" and an "electroless method", and these two methods are already used. However, the mechanism of the treatment bath differs between "electrolysis" and "electroless".

More specifically, in the case of "electroplating", each component in the solution does not react. The reaction is an electrochemical reaction using an external power source as a reaction energy source. Furthermore, no chemicals (reducing agents) are used to chemically promote the electrolytic reaction during the "electroplating" process.

In contrast, in the case of electroless plating, each component in the solution reacts. Moreover, without using an external power source as a reaction energy source, the electrochemical reaction involves the reduction of metal ions in a solution (cathodic reaction) and the oxidation of reducing agents (chemicals with little dissociation of aqueous solution) added to the solution ( Anode Reaction: Uses electrochemical energy (energy to generate potential difference by chemical reaction) generated during anodic reaction.

By "plating", a metal film is formed in the reduction reaction of metal ions (cationic), and a phosphate film is formed in the oxidation reaction (dehydrogenation reaction) of phosphate ions (anion) in the phosphate chemical conversion treatment.

The present invention relates to an electrolytic phosphate chemical treatment method and a composite film formed on the steel surface.

1 is a schematic diagram showing an outline of an electrolytic treatment.

2 is a schematic diagram of an electrolytic reaction system.

3 is a block diagram showing the configuration of an electrolytic phosphate chemical treatment apparatus.

4 is a perspective view of the object to be treated in Example 1 and Comparative Example 1. FIG.

5 is an EDX analysis chart of the planar portion of the workpiece in Example 1. FIG.

6 is an EDX analysis chart of the outer peripheral portion of the object to be treated in Example 1;

7 is an EDX analysis chart of the planar portion of a workpiece in Comparative Example 1. FIG.

8 is an EDX analysis chart of the outer peripheral portion of the object to be treated in Comparative Example 1. FIG.

Fig. 9 is a GDS analysis chart of the planar portion of the workpiece in Example 1;

10 is a GDS analysis chart of an outer circumferential portion of an object to be treated in Example 1;

11 is a GDS analysis chart of a planar part of a workpiece in Comparative Example 1. FIG.

12 is a GDS analysis chart of the outer circumferential portion of the target object in Comparative Example 1. FIG.

13 is a perspective view of the object to be treated in Example 2 and Comparative Example 2. FIG.

Fig. 14 is an EDX analysis chart of the planar portion of the workpiece in Example 2;

Fig. 15 is an EDX analysis chart of the planar portion of a workpiece in Comparative Example 2;

Fig. 16 is an EDX analysis chart of the planar portion of the workpiece in Example 3;

Fig. 17 is an EDX analysis chart of the outer peripheral portion of the object to be treated in Example 3;

18 is an EDX analysis chart of the planar portion of a workpiece in Comparative Example 1. FIG.

Fig. 19 is an EDX analysis chart of the outer peripheral portion of the object to be treated in Comparative Example 1;

20 is a SEM photograph of a planar portion of a workpiece in Example 3. FIG.

21 is a phosphorus analysis photograph of a planar part of a workpiece in Example 3;

22 is a zinc analysis photograph of the planar portion of the workpiece in Example 3. FIG.

23 is a nickel analysis photograph of the planar portion of a workpiece in Example 3. FIG.

24 is an iron analysis photograph of a planar portion of a workpiece in Example 3. FIG.

25 is a SEM photograph of the outer peripheral portion of the object to be treated in Example 3. FIG.

Fig. 26 is a phosphorus analysis photograph of the outer circumference of the object to be treated in Example 3;

27 is a zinc analysis photograph of the outer peripheral portion of the object to be treated in Example 3. FIG.

28 is a nickel analysis photograph of the outer circumferential portion of the target object in Example 3. FIG.

29 is an iron analysis photograph of an outer circumferential portion of an object to be treated in Example 3;

Next, the above-described actions and effects will be described in detail while comparing with the prior art.

First, according to Japanese Patent No. 5-822481, which discloses a conventional electrolytic phosphate chemical treatment method, each component of the phosphate chemical treatment bath having the same composition as the electroless phosphate chemical treatment is used.

That is, the treatment bath in the conventional electroless phosphate chemical treatment is extremely active and the bath composition is easily decomposed to react with each component in the treatment bath to form a film. This is because a reaction in the solution of the treatment bath cannot occur if the treatment bath is not active. In order to activate the treatment bath, that is, chemically decompose (oxidize; dehydrogenate), sodium hydroxide or the like is added to a conventional electroless phosphate chemical treatment bath to adjust the pH (hydrogen ion concentration) within a predetermined range or oxidize nitrite ions. Measures such as addition as an accelerator to promote the reaction were taken. By adding these chemicals, a large amount of Na ions are contained in the phosphate chemical treatment, and eventually, a large amount of impurities (unnecessary substances) are not contained in the electroless phosphate chemical treatment bath.

The conventional electrolytic phosphate chemical treatment method uses such a phosphate chemical treatment bath containing components other than the film component. Therefore, these components other than the coating component suppress the formation of the phosphate chemical conversion coating formed on the surface of the workpiece, and therefore cannot form the coating efficiently on the surface of the treatment portion.

In contrast, the phosphate chemical treatment bath of the present invention has a concentration of 400 ppm or less, preferably 100 ppm or less, in a phosphate chemical treatment bath of ions such as Na ions, which are metal ions other than the film component, which are not involved in the film forming reaction. It is. As a result, the stability of the treatment bath is considerably improved, resulting in a composition that does not produce sludge. Moreover, with this composition, only each component in the solution of the treatment bath reacts at the electrode surface during the electrolytic treatment, while the treatment bath only reacts at the electrode surface during the electrolytic treatment at any other time or at different locations. The reaction does not occur substantially.

Further, it is preferable to use the following means as a means for causing the reaction to occur only at the electrode surface during the electrolytic treatment in the treatment bath, and for the reaction not to occur substantially at any other time or at a different position.

That is, one example of such means is to remove a portion of the phosphate chemical treatment bath from a bath having a phosphate chemical treatment bath to thermodynamically stabilize the energy state of a portion of the liquid phosphate chemical treatment bath, and then return it to the bathtub, whereby It is preferable to remove a part of the phosphate chemical treatment bath from the treatment bath and pass it through a filter to remove the solid precipitated during the phosphate chemical treatment in the film formation reaction and return it to the bath.

Moreover, when the workpiece is not in contact with the phosphate conversion bath, a metal material used as the anode during the electrolytic treatment using the workpiece for the cathode while applying a voltage of 5 V or less between the anode and the cathode is used. It is preferable to use for the anode and to use a material which is insoluble in the phosphate chemical treatment bath for the anode, and if the object is not in contact with the phosphate chemical treatment bath, a voltage is applied between the anode and the cathode so that the cathode is substantially It is preferable to use the metal material used as an anode for the cathode during the electrolytic treatment using the object to be treated for the cathode, and to use an insoluble material for the anode in the phosphate chemical treatment bath.

In addition, when each component of the phosphate chemical treatment bath is newly replenished, a part of the phosphate chemical treatment bath is removed, and the treatment bath component is added at least at a concentration higher than the component concentration of each component constituting the phosphate chemical treatment bath with respect to the removed treatment liquid. It is preferable to add a replenishment solution containing to the portion removed from the electrolytic cell.

Further, the composition of the treatment bath during the electrolytic treatment is such that the ratio of the concentration of the phosphate ions and the phosphoric acid (g / l) to the concentration (g / l) of the metal ions forming the complex with the phosphate ions is 0.1 or more. It is preferable.

By implementing the above measures, the phosphate chemical treatment bath is substantially free of solids that affect the film formation reaction. During the electrolytic treatment, the reaction takes place only at the electrode surface, while the reaction is substantially conducted at other times and at other positions. Does not happen.

In addition, in the "electrode phosphate chemical treatment method" of the present invention, in the "electrodeposition coating" in which each component is reacted in a solution to form a coating, even though extreme care should be taken to prevent solidification and decomposition of each component in the solution, As this is an organic type, it is possible to achieve this purpose by preventing the incorporation of impurities and keeping the treatment bath constant at a constant temperature.

Since the "electrolytic phosphate chemical treatment method" of the present invention includes electrolysis in an inorganic acid solution, it is preferable to take the above measures in addition to the measures in electrodeposition coating.

Furthermore, since the present invention contains substantially no metal ions other than the metal ions constituting the film forming component such as Na as in the conventional case, the metal ions forming complexes with the phosphate ions in the phosphate chemical treatment bath are phosphate chemically soluble. It may also be present as a complex in the treatment bath. Therefore, even if metal ions are dissolved in the solution, they are present in a stable form in the treatment bath, so that phenomena such as sludge formation in the treatment bath can be suppressed, and the film deposition reaction can be caused only on the surface of the workpiece.

This is equivalent to the cyano complex which is often used in conventional electroplating, because the cyano complex does not decompose in solution, but rather decomposes in the form of a metal film on the surface of the cathode where charge is concentrated. .

Moreover, in the past, complexes have also been used in conventional electroless phosphate chemical treatment baths. That is, metal ions (such as Fe ³⁺ , Zn ²⁺ or Mn ²⁺ ) that precipitate as phosphate compounds on the metal surface are dissolved in solution by forming complexes with phosphate ions. However, since the phosphate ion complex used in the conventional electroless phosphate chemical treatment bath contains ions such as Na ions, and thus becomes active (unstable), the stability of the complex is lower than that of the cyano complex used in electroplating. . Therefore, even in the case of the electroless treatment, the complex is easily dissolved to form a film and sludge, so the present invention cannot be used in any of these methods in this treatment.

Moreover, the cyano complex is stable with respect to the complex stability, and in the case of electroless treatment (electroless plating), the complex does not dissolve (decompose). For this reason, cyano complexes are only used in electroplating.

If the stability of the phosphate ion complex can be increased, the complex does not readily degrade. The reason is that the pH of the conventional electroless phosphate chemical treatment bath must be adjusted (add Na ions etc. for that purpose), so the stability of the phosphate ion complex used in the treatment bath is low and eventually the phosphate ions are easily dissolved (oxidized). (By decomposition). In the electrolytic phosphate chemical treatment bath, the pH adjustment of the bath is not performed by adding Na ⁺ . For this reason, the stability of the phosphate ion complex can be increased. In the case of a treatment bath having a large stability of the phosphate ion complex, decomposition does not occur without electrolysis and film formation does not occur. Furthermore, as in the case of electroplating at the time of electrolysis, there is no decomposition of the phosphate ion complex in the solution, and since the phosphate ion complex decomposes only on the cathode surface where the charge is concentrated, there is essentially no sludge formation and a treatment bath. It remains transparent.

If the pulling ion complex is too stable, it is not suitable for forming a film by cathode electrolysis. For this reason, the stability of the phosphate ion complex must be maintained within an appropriate range.

In order to achieve this in the present invention, the composition of the treatment bath during electrolytic treatment is determined by the concentration of the metal ions forming a complex with the phosphate ion (g / l) relative to the ratio of the concentration of the phosphate ion and the phosphoric acid (g / l). It is preferable to make ratio of 0.1 or more. Therefore, the stability of the complex can be secured.

[Review of Characteristics of Electrolytic Phosphate Chemical Treatment]

In addition to the purification methods such as the prevention of impurity incorporation and the treatment of filtration and complexes in the treatment bath, it is necessary to use measures to accommodate the unique characteristics of the electrolytic phosphate chemical treatment in order to utilize the electrolytic phosphate chemical treatment practically.

These unique features are described below.

In the electrolytic phosphate chemical treatment of the present invention, the above-described phosphate chemical treatment method includes the steps of performing electrolytic treatment using the above-mentioned to-be-processed object for an anode and then subjecting the to-be-processed material to a cathode for electrolytic treatment. It is preferable to include.

In this case, it is preferable to use a film forming metal (such as Fe, Ni or Zn) for the anode and to use the workpiece for the cathode.

Furthermore, two cases in which metal material is installed as an anode in an electrolytic cell are shown below.

(1) A metal in which the electrode material is dissolved to form a film forming component

(2) Insoluble materials in which electrode materials do not dissolve or only slightly dissolve

The cathode electrolytic treatment uses two of the above electrode materials or only one of them. A summary of these classifications is shown in Table 3.

[Table 3] Cathodic Electrolytic Treatment

Type of anode material Cathode electrolytic voltage Remarks (1) Metallic materials which easily dissolve and precipitate to form coatings Less Materials to Form Phosphate Compounds Fe, Zn Metal ions dissolved in the solution are reduced and readily dissolved and precipitated as a metal element Cu (2) extremely slightly soluble or insoluble materials; greatness Material with high melting voltage that does not form phosphate Ni and other insoluble materials

In the case of (1) in which a metal which is dissolved and becomes a coating component is used for an anode, the anode material is electrochemically dissolved by the action of an external power source and is present in the ionic state dissolved in the solution, and then precipitates at the cathode. Solidification) to form a film.

In the case of (2) in which an insoluble material which is insoluble or extremely insoluble is used for the anode, cations dissolved in the solution are precipitated at the cathode by acting by an external power source. These cases are used depending on the nature of the phosphate chemical coating formed.

As shown in Table 3, "metals forming phosphate compounds (such as Fe and Zn)" dissolve and precipitate relatively easily (at low voltage) even under conventional phosphate chemical bath conditions as shown in the electroless treatment. However, as a metal which becomes "a solid substance in which metal ions dissolved in a phosphate conversion bath is reduced to precipitate as a metal element", metals (e.g., Cu) readily dissolved and precipitated under the conditions of a conventional electroless phosphate conversion bath and dissolved and precipitated Include metals (such as Ni) that require large voltages and currents.

When a metal (for example, Ni), which requires a large voltage and current for melting and precipitation, is added to a treatment bath to dissolve and precipitate from an electrode serving as an anode, a large voltage and current are required. In this electrolytic treatment, a relatively large voltage and current must be applied to the entire treatment bath. However, such an electrolytic treatment (which requires a large voltage and a current) is not suitable for the electrolysis of metals (Fe and Zn) which apply a low voltage to electrolytically precipitate a phosphate compound.

The inventors have recognized that essentially two systems exist for "cathode electrolysis" as a feature of the electrolytic phosphate chemical treatment. In addition, the present inventors thought that these two cathode electrolytic treatment systems should be used properly by recognizing that there is a difference between these two systems depending on the required properties of the film. That is, the composition of the metal material and the treatment bath used for the anode is determined according to the required coating, and electrolytic treatment (voltage and current) is appropriately used in accordance with the treatment bath and the electrode material.

Recognizing that cathodic electrolysis can be fundamentally classified into two systems suggests that it is necessary to accommodate two systems for the practical application of electrolytic phosphate chemical treatment. In other words, different acceptance conditions are required in the case of using a "metal material which easily dissolves and precipitates and becomes a coating component" and "an extremely slightly soluble or insoluble material".

In the case of using a metal material (e.g., Fe, Zn or Cu) which is easily dissolved and precipitated as a coating component as shown in Table 3 for the anode, in the phosphate chemical treatment bath without applying a voltage (without electrolysis), These metals dissolve easily. If this phenomenon (action) is left as it is, these metal ions are dissolved in the treatment bath even when the treatment is not performed. As a result, the state of the process bath becomes a state in which the process cannot be performed. Thus, there is a need for means to suppress such dissolution. This is the first response to take.

It is preferable to take the following countermeasures as specific examples of measures to be taken as means for suppressing dissolution.

(1) The surface area of the metal electrode (anode) is adjusted during the electrolytic treatment.

(2) The electrolytic current of the metal electrode (anode) is controlled during the electrolytic treatment.

(3) When the electrolytic treatment is at rest (hereinafter simply referred to as "pause electrolysis"), a metal electrode (e.g. Fe, Zn, Cu) which uses an insoluble electrode for the anode and readily dissolves for the cathode Weak electrolytic treatment (pause electrolytic treatment) to the extent that the metal used for cathode does not dissolve (so that each solution component does not decompose) while using.

The second countermeasure is for the use of "extremely slightly soluble or insoluble materials".

For example, in the case of a metal (for example, Ni) in which sufficient dissolution cannot be obtained even when electrolytically using an anode metal, even if necessary as a coating component, all of the metal ions necessary for the coating component cannot be obtained by dissolving from the electrode. In this case, it is preferable to supply the metal ions to the treatment bath by adding the dissolved metal ions to the treatment bath. It is intended for the cathode electrolytic treatment only at the electrolytic reactions (reduction and precipitation) at the cathode. In this case, for example, the electrolytic voltage for bonding Ni in the coating component can be reduced as compared with the case of dissolving Ni from the anode to form the coating. This approach is desirable in practical applications of electrolytic phosphate chemical treatments.

[Reactions Comprising Electrolytic Phosphate Chemical Treatment]

The present invention forms a novel electrochemical phosphate chemical reaction by maintaining the environment for carrying out the electrolytic phosphate chemical treatment. This is outlined below.

[General Recognition of Cellochemical Reactions]

The phosphate chemical conversion reaction of the present invention is essentially free of sludge production. The electrochemical reaction system consists of an anode reaction and a cathode reaction. The anode reaction is an oxidation reaction occurring at the anode. Moreover, the cathode reaction is a reduction reaction occurring at the cathode. In the electrochemical reaction system, the electrode potential is defined as that the cathode reaction is higher than the anode reaction.

It is also believed that when an anode reaction occurs at the anode, the corresponding solvent and anion are cathodic. It is believed that when a cation cathodes, the corresponding solvent and anion undergo an anode reaction.

The outline of the electrochemical reaction system formed in the electrolytic treatment is shown in FIG.

As shown in FIG. 2, electrochemical reaction systems are classified into two types: (1) "reaction systems between electrodes separated in solution" and (2) "reaction systems on the same electrode surface not separated in solution".

The "reaction system between electrodes separated in solution" of (1) forms an anode-cathode reaction system between the separated electrodes. This reaction system is formed by dividing as follows.

(1) -1 Electrochemical reaction system involving cations between electrodes (cathode reaction at anode and anode reaction at cathode)

(1) -2 Electrochemical reaction system involving anion and solvent between electrodes (cathode reaction at anode and anode reaction at cathode)

"Reaction system on the same electrode surface not separated in solution" of (2) is an anode-cathode reaction system formed mainly between cations, anions and a solvent on the same electrode surface. This reaction system is formed by dividing as follows.

(2) -1 anode reaction of cation on anode surface and cathode reaction of anion and solvent

(2) -2 cathode reaction of cation on cathode surface and anode reaction of anion and solvent

When an electrochemical reaction system is formed irrespective of "electroless treatment" or "electrolytic treatment", an electrochemical reaction system composed of a cathode reaction and an anode reaction is formed. However, the electrochemical reaction system of "electroless treatment" consists mainly of cathode and anode reactions on the same surface. In FIG. 2 they are reactions of (2) -1 and (2) -2 and are composed between metal (solid) and solution (liquid).

In some cases, the electrochemical reaction system may consist of a pair of cathode and anode reactions, and in some cases, the electrochemical reaction system may consist of a plurality of pairs of cathode and anode reactions. As shown in FIG. 2, the electrochemical reaction system of phosphate chemical treatment is a complex system composed of a plurality of pairs of cathode and anode reactions. This complexity makes it difficult to control the reaction system.

[Configuration of Electrochemical Reaction System in Electrolytic Phosphate Chemical Treatment]

In the case of the "cathode electrolytic treatment" of the electrolytic phosphate chemical treatment, when Fe, Zn, Ni or Cu is used as the film forming metal electrode (anode), the reaction is configured as shown in Table 4. Further, in the example below, iron (steel material) is treated with a phosphate chemical treatment bath (phosphate chemical treatment bath) containing zinc ions, nickel ions, phosphate ions and nitrate ions.

[Table 4] Classification of Electrolytic Phosphate Chemical Treatment Reaction (cathode treatment)

Anode reaction Cathode reaction Anode surface 1. Dissolution (oxidation) reaction of metal electrode (Fe, Zn, Ni, Cu, etc.) Fe → Fe ²⁺ + 2e (-0.44V) (1) Zn → Zn ²⁺ + 2e (-0.77V) (2) Ni → Ni ²⁺ + 2e (-0.23V) (3) Cu → Cu ⁺ + e (0.52V) (4) Fe ²⁺ → Fe ³⁺ + e (0.77V) (5) 1. The reduction of the nitrate-based _{^{(NO 3 - → NO 2 -}} → NO) NO 3 - + 3H + + 2e → HNO 2 + H 2 O (0.94V) (6) NO 3 - + 4H + + 3e → _{NO + 2H 2 O (0.96V)} (7) NO 3 - + 2H + + 2e → NO 2 - + H 2 O (0.84V) (8) 2. Reduction of water (solvent) O ₂ + 4H ⁺ + 4e → 2H ₂ O (1.23V) (18) Cathode surface (surface of workpiece) 1. Oxidation reaction of the phosphoric acid-based ion _{(H 3 PO 4 → H 2} PO 4 - → PO 4 3-) H 3 PO 4 → H + + H 2 PO 4 - (9) H 2 PO 4 - → 2H + + PO ₄ ^3- (10) 2. Crystallization reaction in which the metal ions are combined with phosphate ions and do not change their charges (Zn, Fe, Mn, Ca ions, etc.) 2PO ₄ ^3- + 2Zn ²⁺ + Fe ²⁺ → Zn ₂ Fe (PO ₄ ) ₂ ( 11) M ^{X +} (metal ion) + n (PO ₄ ^3- ) → M (PO ₄ ) (12) 3. The oxidation reaction of water ^{_{(solvent) H 2 + 2OH - → 2H}} 2 O + 2e (-0.83V) (19) 1. Reduction of metal ions with change in charge [Reduction reaction of ions such as Ni, Cu, (Fe, Zn)] Ni²⁺+ 2e →Ni(-0.23V) (13) Cu⁺+ e →Cu(0.52V) (14) Fe²⁺+ 2e →Fe(-0.44V) (15) Zn²⁺+ 2e →Zn(-0.77V) (16) Fe³⁺+ e → Fe²⁺(0.77V) (17) (Note) The underlined parts show the film forming components.

As described above, the electrochemical reaction between electrodes through an external power source is basically two systems. The first is a reaction system between the dissolution reaction of the film-forming metal (electrode) at the anode (anode reaction) and the precipitation reaction (cathode reaction) of dissolved metal ions at the cathode (treatment) surface. The other reaction system is an electrochemical reaction system on the same electrode surface. This is a dissolution (oxidation) reaction of the metal at the anode and a reduction reaction of the solution components (nitrate ions and water), an oxidation reaction of the solution components (phosphate ions and water) at the cathode and a reduction reaction of the metal ions. Furthermore, ions of metals (such as Zn, Fe or Mn), which form phosphate complexes due to the oxidation reaction (dehydrogenation) of phosphate ions on the surface of the cathode, precipitate on the surface of the cathode.

[Electrochemical Reaction of Phosphate Chemical Reaction-1 (Electrolytic Treatment)]

In the electroless phosphate chemical reaction, the anode and cathode reactions shown in the above table are carried out in the same plane without polarization of the anode and cathode.

The reason why the electroless phosphate chemical conversion treatment is mainly performed only for steel materials is that the environment is formed so that an electrochemical reaction system is formed simultaneously even without electrolysis between the phosphate chemical treatment bath and the steel material.

Furthermore, when the workpiece is copper (Cu), chlorine ion (Cl ⁻ ) is added. In addition, when the to-be-processed object is aluminum (Al), fluorine ion (F <^-> ) is added. The addition of fluorine ions (F ⁻ ) dissolves (oxidizes) Al and forms an electrochemical reaction system in connection with the phosphate chemical treatment (even if electroless) in the treatment bath. Therefore, the phosphate chemical film is formed in the same manner as steel. However, the fluorine ions (F ⁻ ) are neither bonded to the coating nor removed from the solution by the reaction by reducing (NO ₃ ⁻ → NO) and evaporating (gasification), such as nitrate ions. Therefore, when the fluorine ion exceeds a predetermined concentration, it is necessary to prepare a new treatment liquid.

In the case of electroless phosphate chemical treatment, the electrochemical reaction system is formed on the same surface, so that the dissolution of the material (the workpiece) is limited when the film is formed. Therefore, it cannot thicken without destroying a film. If the reaction is continued in a group to obtain a thick film, the reaction is accompanied by the dissolution of the material (treated matter) and thus becomes a crude film. It is for this reason that the thick film formed from the electroless treatment (heating bath) and used for the cold forging press working base treatment is coarse.

Moreover, since the electroless phosphate chemical conversion reaction is an electrochemical reaction on the same surface without using an external power source, the reduction and precipitation of metal ions due to charge change are extremely limited. Therefore, even in a treatment bath containing Ni ions, the reduction and precipitation of Ni are only a few. (Precipitation of Ni is possible only in the initial film formation step when Fe is dissolved.) Therefore, the film formed is mainly phosphate. This is the basis for calling the conventional electroless treatment phosphate chemical treatment.

[Electrochemical Reaction of Phosphate Chemical Reaction-2 (Anode Electrolysis)]

When the film is formed by the anode electrolytic treatment in the electrolytic phosphate chemical treatment, the reaction system is basically the same as the electroless treatment. The action of the anode electrolysis is to promote the "dissolution (oxidation) reaction of the metal electrode" shown in Table 4. The "dissolution (oxidation) reaction of a metal electrode" is the first reaction to initiate a phosphate chemical treatment (film formation) reaction system. This reaction (dissolution reaction of the object to be processed) is easily and surely performed by the anode electrolytic treatment. As a result, the formed phosphate film is excellent in adhesion to the workpiece (material). However, it is not possible to thicken the film.

In the case of forming the film by the anode electrolytic treatment followed by the cathode electrolytic treatment, the role of the anode is limited to the dissolution (oxidation) reaction of the metal electrode and the reduction reaction of water. In the anode electrolytic treatment, dissolution of the workpiece takes place reliably, and the film is formed in the next cathode electrolytic treatment.

For this reason, when the film is formed only by the anode electrolytic treatment, the composition of the treatment bath is different from the case where the film is formed by using the anode electrolytic treatment and the cathode electrolytic treatment together.

Furthermore, in the case of coating only by the anode electrolytic treatment, a material for the cathode serving as a counter electrode which does not dissolve in the phosphate chemical treatment bath is selected. For this reason, materials such as titanium that do not dissolve in the chemical conversion bath are used for the cathode.

[Electrochemical Reaction in Phosphate Chemical Reaction-3 (Anodization)]

In the electrolytic phosphate chemical treatment, a method of using anodization and cathodic treatment together is usually employed. In this case, the function of the anodization is to dissolve the surface of the workpiece and to secure the adhesion of the coating. Cathodic treatment is to form a film.

Furthermore, in certain cases, anodization may be omitted. Electrolytic phosphate chemical reactions are not electroless if the film does not require firm adhesion and the pH of the electrolytic phosphate chemical treatment bath is lower than that of conventional electroless treatment baths. If it is also carried out in the can be omitted.

In the conventional electroless phosphate chemical treatment, the "dissolution reaction of the object" and "the reaction related to film formation" occur on the same surface. However, in the cathode electrolytic treatment of the present invention, as shown in Table 3, "dissolution reaction of the workpiece" does not occur on the surface of the workpiece to be the cathode. And only the "response with respect to film formation" occurs on the surface (cathode) of the workpiece.

Electrochemical reaction system related to cathodic electrolysis treatment has three reaction systems according to the classification shown in FIG.

i. Oxidation-reduction (dissolution-precipitation) reaction system for metal ions between electrodes (anode-cathode) [FIG. 2 (1) -1]

ii. Oxidation-reduction reaction system for anion and solvent (water) between electrodes (anode-cathode) [FIG. 2 (2) -2]

iii. Anodization and Cathode Reaction of Anion and Solvent (Water) on the Surface of Cathode [Fig. 2 (2) -2 and (1) -3]

These reaction systems are demonstrated.

i. Oxidation-reduction (dissolution-precipitation) reaction system for metal ions between electrodes (anode-cathode) [FIG. 2 (1) -1]

This interelectrode reaction is formed by the cathode reaction (reduction and precipitation of metal ions) on the cathode surface and the anode reaction (dissolution of metal) on the anode surface. This reaction occurs when an external power source is used. The cathode surface is subjected to a large electrochemical energy during the cathode reaction, and thus the precipitation reaction is accompanied by a change in charge (reduction). The cathode precipitation reaction is a precipitation reaction involving a change (reduction) of a charge of metal ions such as nickel, copper, iron, or zinc. The metal ions are bonded to the underlying metal by an action similar to that of electroplating. Furthermore, even though the metals forming the film by iron or zinc phosphates preferentially precipitate as phosphates irrespective of the charge change, the precipitation potential and dissolution accompanying the charge change are more than the anode reaction potential of water (-0.83 V). By changing the charge, the metal can be precipitated.

ii. Oxidation-reduction reaction system for anion between the electrode (anode-cathode) and solvent (water) [(1) -2 and (1) -3 of Fig. 2]

This interelectrode reaction involves the anodic reaction [dissociation and oxidation of phosphate ions, the formation of phosphate and oxidation of solvent (water)] on the cathode surface, and the cathode reaction [reduction of nitrate ions and solvent (water) on the surface of the anode. Reduction]. The phosphate crystals produced by the formation of such an electrochemical reaction system are electrochemically bound to the cathode surface.

iii. Anodization and Cathode Reaction of Anion and Solvent (Water) on Cathode Surface [Fig. 2 (2) -2]

This reaction system is characterized by the oxidation reaction of water on the cathode surface [anode reaction in equation (19)] and the cathode precipitation reaction according to the change (reduction) of charge on the cathode surface [Equations (13), (14), (15) And (16)]. The reaction system is formed to reduce the dissolved ions in the phosphate conversion bath to precipitate as a metal (dissolution-precipitation equilibrium potential) of metals having a potential of -0.83 V (hydrogen standard electrode potential), which is equal to the anode decomposition reaction of water. It can be deposited. As described above, in the electrochemical reaction system, the cathode reaction potential is defined to be higher than the anode reaction potential. The formation of this electrochemical reaction system thus demonstrates that the precipitation of metal ions having a dissolution-precipitation equilibrium potential of zinc [dissolution-precipitation equilibrium potential (hydrogen standard electrode potential) = -0.77 V] or more is possible in the present invention. That is, the metal precipitated at the cathode is determined.

This means that metals with low dissolution-precipitation equilibrium potentials such as sodium [dissolution-precipitation equilibrium potential (hydrogen standard electrode potential) = -2.7 V], potassium [dissolution-precipitation equilibrium potential (hydrogen standard electrode potential) = -2.9 V] are electrolyzed. This implies that precipitation is impossible and does not participate in film formation. For this reason, these metal ions interfere with the electrolytic coating film formation.

Moreover, although Zn, Fe and the like can theoretically change their charges to precipitate as metals, Zn, Fe and the like are typically present in the treatment bath by forming complexes with phosphate ions. In terms of energy, it is more preferable to precipitate as phosphate. For this reason, Zn, Fe, and the like preferentially exist as phosphates in the coating.

In addition to the coating components described above, the metal ion is about 0 to 400 ppm, preferably 0 to 100, and in the cathode electrolytic treatment of the present invention, the treatment is substantially free of solids that affect the film forming reaction. For this reason, the metal which does not form a phosphate can be contained in a composite film, and the composite film itself can be made close to the property of the conventional "plating". Therefore, the formed phosphate chemical conversion film is subjected to a high level of electrochemical energy, so that the phosphate chemical conversion film can be reliably fixed to the negative electrode (the workpiece).

In the present invention, an oxidation-reduction (dissolution-precipitation) reaction system relating to metal ions between the electrodes (anode-cathode) is continuously formed by connection of an external power source. Thus, ions of Ni and other metals can be reduced and precipitated and distributed during the entire film formation process. Moreover, it becomes possible to contain only a specific metal, or to not contain any metal. That is, it is possible to control the cathodic coating formation reaction.

[Features of electrolytic phosphate chemical conversion film]

In the present invention, it is remarkable that the metal accompanying the charge change can be deposited throughout the entire film formation. This is the same phenomenon as "electroplating".

In other words, the electrolytic phosphate coating may be referred to as a "phosphate-containing composite electroplating coating". In other words, the ratio of the atomic number concentration is such that the metal which does not form phosphate (for example, Ni) contains at least 1/4 of phosphorus (P) serving as an phosphate-forming element so that the film is formed on the outermost surface of the phosphate film. Can be formed. (Refer to EDX film analysis results of Table 10 and Example 1 and EDX film analysis results of Table 16 and Examples 4 and 5.) This film is an electroless which forms a conventional film by using the crystallization action of phosphate. It is a film that cannot be realized by the treatment.

(The ratio Ni / P = 1/4 of atomic number concentration corresponds to the fact that Ni / Zn ₃ (PO ₄ ) ₂ is present at a ratio of 1/2.)

Furthermore, by not performing the cathode electrolytic treatment of the metal accompanying the charge change, the precipitation of the metal accompanying the charge change can be completely eliminated in the same manner as the electroless treatment. (See Table 12 and Example 2 EDX film analysis results.)

Moreover, another feature of the electrolytic phosphate chemically treated film of the present invention is that when the film is analyzed by X-ray, it is found that a film having no peak corresponding to the phosphate crystal is formed. (See Example 3 in Table 16, Figs. 16 and 17.) This is also possible because a metal (for example, Ni) accompanying charge change can be precipitated through the whole of the film formation. In other words, it is thought that phosphate crystals are precipitated in accordance with precipitation of metals (for example, Ni) accompanying charge change, and phosphate crystals are thought to be finely dispersed in the metal component. Even if the film of Example 3 is a film containing phosphorus (P) and Zn and containing a phosphate, the phosphate crystal is dispersed together with the Ni metal. This is shown in the EPMA elemental analysis photograph (Table 17, FIGS. 20-29) taken in the cross-sectional direction of the film. This coating is called "phosphate-containing composite electroplating coating".

As described above, the present invention has developed an electrolytic phosphate chemical conversion treatment suitable for the general principle of the electrochemical reaction.

That is, the present invention can provide a phosphate chemical treatment method for forming a phosphate chemical coating film capable of forming a film made of phosphate and metal from a film mainly composed of conventional phosphate crystals.

Moreover, the composite film obtained in the present invention may contain a metal material other than phosphate.

Therefore, by this novel phosphate chemical treatment, a composite film that can be applied to many metal materials can be obtained by the same method of applying electroplating regardless of the type of metal.

[Configuration of Electrolytic Phosphate Chemical Treatment]

The electrolytic phosphate chemical treatment is roughly divided into (1) apparatus, (2) treatment bath composition, (3) electrochemical conditions of treatment bath, and (4) electrolytic method.

First, the apparatus used for the electrolytic phosphate chemical treatment method of the present invention will be described with reference to FIG.

3 shows the configuration during the cathode electrolytic treatment.

Where (1) is the phosphate chemical treatment bath of the present invention, (2) is the object to be treated, (3) and (4) are the working electrodes, and (3) forms a complex with phosphate in the phosphate chemical treatment bath. (4) is a working electrode composed of a metal material, and (4) is a potential at which the ions dissolved in the phosphate chemical treatment bath are reduced and precipitated as a metal is not less than -0.83 V (denoted as a hydrogen standard electrode potential), which is the anode electrolytic reaction potential of water as a solvent. It is a working electrode composed of a metal material.

Furthermore, (5) is a power source for applying a voltage between the workpiece 2 and the working electrodes 3, 4, and (6) is a phosphate chemical treatment bath (1) from inside the bathtub having the phosphate chemical treatment bath (1). Is a filtration / circulation pump that thermodynamically stabilizes the energy state of the liquid in the phosphate chemical treatment bath (1) by removing a portion of), and (7) removes solids deposited in the phosphate chemical treatment bath (1) during the film formation reaction. Is a filter.

(8) is a resting electrolytic anode made of an insoluble material with respect to the phosphate chemical treatment bath used when the object is not in contact with the phosphate chemical treatment bath, and (9) the phosphate chemical treatment bath (1). It is a replenishment chemical at a concentration higher than the concentration of each component of (10), and (10) is a replenishment chemical pump for adding a replenishment chemical to a treatment bath.

Denoted at 11 is a control computer that controls the amount of application of the replenishment chemical, the applied voltage, and the like in accordance with information from the sensor 12 measuring pH, ORP and other parameters of the treatment bath.

Hereinafter, the present invention will be described with reference to FIG. 3.

In this invention, the to-be-processed object is connected to the cathode by DC power supply, and the electrode (working electrode) which consists of metal or electroconductive material which forms a phosphate film is connected to the anode. Further, the workpiece to be treated is connected to the anode and the conductive material during the anode electrolytic treatment.

In the case of the anode electrolytic treatment, there is only one working electrode [counter electrode].

In the case of cathode electrolytic treatment, there may be only one working electrode, but a plurality of electrodes may be used. Moreover, it is preferable to install and use a DC power supply for electrolysis of each working electrode. This is a phenomenon in which a large amount of current flows in an electrode disposed at a position where current easily flows when a plurality of identical electrodes are connected to a single DC power source, while no current flows in an electrode disposed at a position where current does not easily flow. It is to prevent this from happening.

A resting electrolytic electrode is installed in the electrolytic cell. This resting electrolytic electrode (anode) uses a conductive material that does not dissolve in the treatment bath. The role of this electrode is to prevent the dissolution of the working electrode when the workpiece is not treated (when the electrolyte is at rest). When the electrolysis is at rest, this insoluble conductive material is used as an anode and a working electrode is used as a cathode, and these are connected to a direct current power source. In this case, only a slight electrolysis occurs so as not to dissolve the working electrode. This electrolysis is called resting electrolysis. Due to such resting electrolysis, the electrodes are not dissolved in the treatment bath when the electrolyte is at rest, thereby preventing decomposition of the treatment bath.

A circulation pump is used to filter and circulate the treatment bath. Moreover, a filter is used to remove the resulting slurry. When the electrolytic treatment is completed and the current to the workpiece is interrupted, a phenomenon in which charge accumulated in the workpiece is released into the treatment bath occurs. At this time, part of the film is released into the treatment bath. When this accumulates, sludge is formed. If this phenomenon continues, sludge will continue to form. Filtration and circulation of the treatment bath will suppress these phenomena.

A pH electrode, an ORP electrode, an EC (electrical conductivity) electrode, a thermometer electrode, etc. are installed in a sensor electrode tank. Since the electrolytic current flows in the processing tank, these electrodes cannot be provided in the processing tank. Therefore, these must be installed separately.

A chemical tank and a chemical pump are installed for chemical addition. It is desirable to add the chemical to a portion of the tank that flows away from the electrolyzer in the filtration and circulation paths of the treatment bath. The reason for this is that even when in the electrolytic cell, the hydrolysis occurs little by little at all times, making the electrolytic cell extremely electrochemically active. Therefore, if an active chemical having a higher concentration than the treatment bath is added to the tank in this active state, This is because the component ions react to easily generate sludge.

A control computer is installed to properly conduct the electrolytic treatment (reaction).

The dissociation degree of phosphoric acid is described below. The pH of the electrolytic phosphate chemical treatment bath of the present invention is 0.5 to 5.0. The owner of the change in the phosphate conversion bath is the dissociation of phosphoric acid (H ₃ PO ₄ ), which is one of the components of the treatment bath (phosphate conversion bath). That is, phosphoric acid (H ₃ PO ₄ ) dissolves, but the dissociation coefficient (pKa) of phosphoric acid becomes large. The acid dissociation coefficient (pKa) is the logarithm of the inverse of the dissociation constant, and the larger the value, the lower the dissociation degree of the acid. In other words, the strength of the acid is lowered.

The dissociation degree of pure phosphoric acid (H ₃ PO ₄ ) is pKa = 2.15, while the dissociation degree of H ₂ PO ₄ ⁻ , where H ⁺ is dissociated from H ₃ PO ₄ , is pKa = 7.2. This indicates that H ₂ PO ₄ ⁻ is weaker than H ₃ PO ₄ .

Even if the treatment bath contains phosphate ions, the ionic state due to electrolysis changes (reduced), as shown below, eventually to phosphate (such as Zn ₂ Fe (PO ₄ ) ₃ ), and then to a coating.

_{H 3 PO 4 → H 2 PO} 4 - → HPO 4 2- → PO 4 3-

For this reason, H ₃ PO ₄ is always dissolved in H ₂ PO ₄ ⁻ in the treatment bath. This means that there is a significant difference in the acid activity of the treatment bath depending on whether the phosphoric acid in the treatment bath is mainly in the form of H ₃ PO ₄ or H ₂ PO ₄ ⁻ .

When phosphoric acid is mainly in the state of H ₃ PO ₄ , the acid activity of the treatment bath is relatively large, and the acid is stabilized in the direction of consuming acid (H ⁺ ) in the treatment bath (the direction in which phosphoric acid dissociates). That is, even if a solution mainly containing H ₃ PO ₄ consumes acid (H ⁺ ), the goal of this consumption is to consume acid (H ⁺ ) by dissolving the Fe electrode immersed in the treatment bath. Due to this action, the treatment bath is decomposed to generate sludge.

In this case, the treatment bath containing mainly H ₃ PO ₄ contains a large amount of acid (H ⁺ ), and the ratio of metal ions dissolved in the treatment bath is correspondingly small as the ratio of acid (H ⁺ ) is high. . Therefore, "metal ions (Zn, Fe, Mn, etc.) component ions which become phosphates and enter the film / (phosphate ions and phosphoric acid)" are relatively small.

On the other hand, when the treatment bath is mainly H ₂ PO ₄ ⁻ , it contains a large amount of metal ions instead of acids (H ⁺ ), and the ratio of metal ions dissolved in the treatment bath is increased. Therefore, the "metal (Zn, Fe, Mn, etc.) component ion which becomes a phosphate and enters the film / (phosphate ion and phosphoric acid)" becomes relatively large.

This can control the ratio of "metal (Zn, Fe, Mn, etc.) component ions which become phosphates and enter the film / (phosphate ions and phosphoric acid)" by the degree of dissociation of phosphoric acid in the treatment bath. That is, the treatment bath can be stabilized during electrolysis by controlling the " metal (Zn, Fe, Mn, etc.) component ions that become phosphates and enter the film / (phosphate ions and phosphoric acid) ”. Metal is a phosphate into the coating reason, focusing on (Zn, Fe, Mn, and so on) component ions these metal ions to phosphate ions (H ₂ PO ₄ ^-) in the solution phosphate ion by forming a complex with (H ₂ PO ₄ ^-) due to stabilize. For this reason, even if ions of metals (Ni, Cu, etc.), which are phosphates, are dissolved, they do not become complexes of phosphate ions (H ₂ PO ₄ ⁻ ) and thus do not contribute to stabilization of the treatment bath.

Furthermore, the ratio of "metal (Zn, Fe, Mn, etc.) component ions which become phosphates and enters the film / (phosphate ions and phosphoric acid)" can be expressed as the ion concentration (g / l) ratio.

Considering the flow during the volume formation, considering the practical application, stabilization of the treatment bath is extremely important.

In the case of an electrolytic phosphate chemical treatment bath containing metal (Zn, Fe, Mn, etc.) component ions which become phosphates and enter into the coating, metal (Ni, Cu, etc.) ions which are not phosphates, phosphate ions, or nitrate ions, The ratio of "concentration (g / l) / (phosphate ion and phosphoric acid concentration (g / l)) of metal (Zn, Fe, Mn, etc.) component ions to be phosphate into the film" is 1/10 (= 0.1) It is suitable to exist in the above range, Preferably it exists in the range of 1/4 (= 0.25)-3.

If the above ratio is 0.1 or more, the ratio of pure phosphoric acid (H ₃ PO ₄ ) in the treatment bath is increased and the stability of the treatment bath is lowered. (Even in Example 1, even though the concentration of Zn ions is 0.4 g / l and the concentration of phosphate ions is 7.6 g / l, the electrolytic amount of Fe is because the surface area of the Fe electrode is 380 cm ² / electrode and the amount of electrolyte is 51A / 8 electrodes. For this reason, "concentration (g / l) / (phosphate ions and phosphoric acid concentration (g / l) of metal ions (Zn, Fe, Mn, etc.) component ions which become phosphates and enters into the coating" is obtained. " The ratio of is to 0.1 or more.)

Further, the upper limit of the above ratio is determined from the viewpoint of "stability in the treatment bath of metal (Zn, Fe, Mn, etc.) component ions which become phosphates and enters the film" and the practical point of view.

In the present invention, the above-described metal ions which become phosphates and enter the film dissolve nitrates to form a solution (treatment bath). Zinc nitrate and manganese nitrate are highly stable compounds. Electrolysis can be performed by adding about 1-10 g / l of phosphate to the zinc nitrate solution or the zinc nitrate + nickel nitrate solution. In this case, the main factor in clouding the treatment bath and inhibiting film formation is the solubility of the solution. In the electrolytic phosphate chemical conversion treatment, even when Zn and Ni are dissolved and treated, zinc nitrate can be dissolved in 100 g / l. Therefore, when limited by solubility, "concentration (g / l) / (phosphate ion and phosphoric acid concentration (g / l)) of metal (Zn, Fe, Mn, etc.) component ions which become phosphates and enter the film" The upper limit of the ratio is about 10 to 100.

Another factor that determines the upper limit is the "practical view". This is based on the fact that the chemical concentration should typically be lowered. Judging from this point of view, the upper limit of the "concentration (g / l) / (phosphate ion and phosphoric acid concentration (g / l)) of metal (Zn, Fe, Mn, etc.) component ions into ginseng salt and into the film" is determined. It is reasonable to say that it is about 4. (However, Fe ions cannot exist as ferrous ions (Fe ²⁺ ) in solution, but only as ferric ions (Fe ³⁺ ), and ferric ions are solidified and added to the treatment bath. When sludge is produced, they cannot be used for replenishment.)

[Process bath composition]

The electrolytic phosphate chemical treatment bath is basically classified into the following components.

That is, the treatment bath is (1) nitrate ion [oxo acid (oxygen) ion containing nitrogen. However, zinc nitrate or nickel nitrate is not dissolved to obtain nitrate ions and is not supplied from nitric acid (HNO ₃ )] and (2) phosphate ions. Furthermore, the treatment bath (1) crystallizes as phosphate in the coating and forms complexes with phosphate ions in the phosphate conversion treatment bath, and metal ions such as zinc, manganese, calcium and iron, and (2) charge change (reduction) of the metal ions. Due to precipitation (encapsulation), the dissolved equilibrium potential of the metal has a cation in the form of ions of metals such as nickel and copper whose anode equilibrium potential of water is -0.83 V (hydrogen standard electrode potential) or more.

The characteristics of the classification of the treatment bath composition are classified into four according to the role of the treatment bath components in the film forming reaction. This aspect (recognition) is not found in the conventional phosphate chemical treatment.

Moreover, components other than the above can also be added as needed. Examples of such a component include fluorine ions in the case of an aluminum material and chlorine ions in the case of a copper material.

In the electroless treatment, the only metal ions in which the charge of the metal ions changed (reduced) and precipitated (encapsulated) were nickel ions in the steel treatment. Moreover, nickel only precipitates at the iron interface and therefore cannot exist on the outermost surface of the coating. This indicates that the precipitation accompanied by the change of the charge of nickel occurs only in correspondence with the dissolution of iron. Nickel does not precipitate because there is no melting of iron other than the steel interface. This shows the characteristics of the conventional electroless coating. In other words, the film obtained from the electroless treatment is a film mainly composed of phosphate.

However, in the embodiment of the present invention, the range of ions of metals such as nickel, in which charges of metal ions change (reduce) and precipitate (encapsulate), can be extended to an environment capable of reducing them in an electrolytic treatment using an external power source. Can be. In electrolytic treatment, in principle, metal ions having a dissolution-precipitation equilibrium potential (cathode precipitation potential) above the anode decomposition reaction of water at the cathode surface (-0.83 V) can be deposited. Examples of the metals corresponding thereto include copper, nickel, iron, zinc, tin, lead, and chromium.

Furthermore, it is preferable that the treatment bath contains only trace amounts (0.1 g / l or less) of the metal ions precipitated (coated) by the change (reduction) of the charge of the metal ions or not. This corresponds to the case where the metal ions degrade the adhesion of the film to the material. It is preferable to form the film used at the time of cold forging work lubrication of steel from the uniform zinc phosphate crystal whose adhesiveness to a material falls. The reason for this is that high adhesion results in poor lubricity. In order to form this kind of film, it should not contain metal ions such as nickel which precipitate due to a change in charge (reduction).

Moreover, the composition of the treatment bath should be as low as possible so that it does not contain substances that are not involved in film formation. For this reason, the incorporation of sodium ions and the like used as degreasing agents should be limited in cations (metal ions). Chemicals added to the phosphate chemical treatment should not contain sodium ions, potassium ions, chlorine ions and sulfate ions (SO ₄ ^2- ).

The content of sodium ions and other unnecessary ions should be as low as possible. As a practical means to do this, the use of soft water should be avoided in the pre-clean phase. It is believed that the concentration of sodium ions and other unnecessary ions in the treatment bath is generally at most 400 ppm, preferably at most 100 ppm.

Next, the preferable composition of each item is prescribed | regulated.

The concentration of nitrate is preferably 6 to 140 g / l, the concentration of phosphate ions and phosphoric acid is preferably 0.5 to 60 g / l, and zinc, manganese, iron or the like forming complexes with phosphate ions in the phosphate conversion treatment bath. The concentration of at least one type of calcium is preferably 1 to 70 g / l, dissolved in a phosphate chemical treatment bath and reduced, and the precipitation potential as a metal is -0.83 V (the hydrogen standard electrode potential, which is the anode electrolysis reaction potential of the solvent as water). It is preferable that the density | concentration of at least 1 sort (s) in the ion of metals, such as nickel, copper, iron, zinc, or chromium more than) is 0-40 g / l.

[Electrochemical Conditions of Treatment Bath]

Parameters defining the electrochemical conditions of the treatment bath are pH, ORP (oxidation-reduction potential), EC (electrical conductivity) and temperature. In electroless treatment, the propulsion energy of the electrochemical reaction depends on the chemical energy of the chemical treatment bath. Therefore, it is necessary to strictly define the electrochemical conditions of the treatment bath that defines the situation of the electrochemical reaction. In electrolysis, however, the propulsion energy of the electrochemical reaction depends on the external power source. In other words, the extent to which electrochemical conditions contribute to the promotion of the reaction is small compared to electroless treatment. Therefore, it is not necessary to strictly define the electrochemical conditions of the treatment bath.

This corresponds to the fact that active electrochemical treatment such as "electroplating" does not actively manage electrochemical conditions. The appropriate range of each item is shown below.

First, as for pH range, 0.5-5 are preferable. The wide range of pH corresponds to the composition of the treatment bath. In principle, the treatment bath of the present invention is an electrolyte bath containing no substance not involved in film formation. Therefore, even at pH 4 or higher, the treatment bath may exist without generating sludge.

ORP (redox potential) of the treatment bath reflects the composition of the treatment bath. Table 3 shows the reaction equations involved in the electrolytic phosphate chemical conversion reaction. The highest reaction potential among them is the cathodic decomposition of water (1.23 V). And the reaction showing the lowest potential is likewise an anode decomposition of water (-0.83 V). Therefore, the ORP of the treatment bath of the present invention is preferably in principle between -0.83 V and 1.23 V. Furthermore, it is preferably in the range of 0 to 1 V (hydrogen standard electrode potential).

EC (electrical conductivity) also reflects the composition of the treatment bath. And the method of measuring conductivity is not strictly standardized. EC is preferably in the range of 4 to 60 mS in the general measurement method.

When only the temperature of a process bath forms a film, it is preferable that it is the range of 10-90 degreeC. The reason is that the treatment bath is stable against heat because it does not contain ions not involved in film formation, and because an external power source is used for reaction promotion, energy can be supplied even in a low temperature region. The practical temperature depends on the composition of the treatment bath.

[Electrolysis Method (Control of Cathodic Electrolytic Phosphate Chemical Reaction)]

The actual control of the cathode electrolytic treatment is carried out by combining three constituent features: selection of the working electrode (anode) material, selection of the treatment bath composition, selection of the electrolytic method and conditions depending on the properties of the film to be formed.

Each configuration feature is described below.

As the working electrode (anode) material, a metal material for forming a film is selected. Examples of such metals are iron, zinc, nickel, copper and the like. In addition to these metals, it is also possible to use manganese-containing alloy materials, calcium-containing alloy materials and magnesium-containing alloy materials that form phosphate compounds. It is also possible to use metallic materials with standard electrode potentials of -0.83 V or higher, such as tin or lead. These metals can be used alone or in combination of a plurality of materials as the anode.

The treatment bath composition (anion and cation) has been described above. However, in the embodiment of the present invention, even if the treatment bath does not contain anions other than nitrate ions and phosphate ions as a general principle, it may contain other ions depending on the kind of material to be treated. For example, in the case of forming a phosphate chemical conversion coating on copper, addition of chlorine ions may be considered. Although this has an effect during anodization, chlorine ions perform the following anode reaction with respect to copper.

^{Cu + Cl - → CuCl + e} (0.137 V) (20)

Since CuCl is contained in the coating, when properly added, chlorine ions do not remain in the treatment bath.

Furthermore, when coating the aluminum material, a small amount of fluorine ions may be added in order to promote the dissolution reaction of the aluminum material. In this case, even if the fluorine ion does not become a coating component, there is an effect of promoting the dissolution reaction of the aluminum material. For this reason, a small amount of fluorine ions is added to supply a part taken from the treatment bath.

The selection of the electrolytic method and condition refers to how much voltage and current is applied between the selected working electrode (anode) and the workpiece (cathode). The choice of electrolytic method and conditions depends on the selected working electrode and the type of film to be formed. In general, two kinds of working electrodes are used, namely "metals crystallized with phosphates (zinc, iron, etc.)" and "metals deposited after reduction of metal ions (nickel, copper, etc.)".

In order to ensure the adhesion with the metal, electrolysis is first performed using a "metal that precipitates after reduction of metal ions (nickel, copper, etc.)" as the working electrode, and then the working electrode alone or by using two kinds of electrodes in combination. Electrolysis is preferably performed using "metals crystallized with phosphate (zinc, iron, etc.)".

In order to ensure the adhesion between the film and the metal, it is preferable to carry out electrolysis only by using "metal which crystallizes with phosphate (zinc, iron, etc.)" as a working electrode.

The typical range of electrolytic voltage is 1-50V, and the typical range of electrolytic current is 0.01-10 A / dm <^2> . Moreover, there is no specific rule for delivery time.

Various coatings can be formed in the cathode electrolytic treatment. For example, a film containing a large amount of zinc can be formed by using a bath containing a large amount of zinc and using a zinc electrode. This coating is applied to the cold forging base.

In addition, a bath containing a large amount of nickel ions is used, and first, the nickel electrode is used for electrolysis, followed by electrolysis using a nickel electrode and an iron electrode, respectively. Can be formed on. The film containing a large amount of nickel is suitable for the base of the coating because it has excellent adhesion with iron base [base].

[Difference with conventional electrolytic treatment]

Table 5 shows the differences from the conventional electrolytic phosphate chemical treatment method in order to clarify the features of the present invention.

The basic difference is the composition of the treatment bath. Whereas the treatment bath of the present invention is a bath free of impurities suitable for reacting each component in the solution during the electrolytic reaction, the treatment bath in the conventional electrolytic treatment contains an impurity that inherits the contents of the electroless treatment bath. There is a significant difference in this respect because it is a swear word.

Table 5 Differences in Electrolytic Treatment Reactions (Prior Art and Invention)

Prior art The present invention Treatment bath composition (1) Phosphate ions, nitrate ions (2) Film-forming metal ions (3) Cations not involved in film-forming (Na ⁺ etc.) (4) Accelerators (nitrite ions, low dissociation ions) (1) phosphate and nitrate ions (2) metal ions for film formation Electrochemical Conditions of Treatment Bath pH = 2 to 4 ORP = 460 to 860 mV Temperature = 20 to 40 ° C pH = 0.5 to 5 ORP = 200 to 1000 mV Temperature = 10 to 90 ° C Electrolytic condition Voltage = 0 to 10 V Current = 0.01 to 4 A / dm ² Voltage = 0 to 50 V Current = 0.01 to 10 A / dm ²

[Investigation of Electrolytic Phosphate Chemical Coating]

Next, the film obtained by this invention is demonstrated.

As described above, the content of the electrochemical reaction of the film forming reaction of the present invention is different from the conventional ones. As shown in the categorization of the cathode electrolysis reaction (Table 4), the content of the electrochemical reaction of the film formation reaction of the present invention is mainly "electrode-electrolysis reaction".

However, the prior art including Japanese Patent No. 5-822481 is not this kind of "electrode-electrolysis reaction". The purpose of the above-mentioned Japanese Patent Application No. 5-822481 is to provide an electrolytic reaction for reinforcing an electrochemical reaction in the conventional electroless phosphate chemical treatment.

The electroless treatment bath is mainly composed of "electrolytic reaction between the object (solid) and the treatment bath (liquid) on the same surface". The difference between the present invention and the electroless treatment is summarized in Table 6.

[Table 6] Difference in Electrolytic Reaction

Electroless treatment Electrolytic Treatment (Invention) Reaction Electrolytic Reaction Method Electrochemical reaction between the object (solid) and the treatment bath (liquid) on the same surface Electrochemical reaction between electrodes in the treatment bath is mainly Electrolysis of Solvent (Water) none has exist Effect on the film Generation mechanism of phosphate crystal Promoter (NO ₂ ^-), reduction in response to the (cathode reaction) phosphate precipitation (oxidation, the anode reaction) of Precipitation by electrochemical reaction between electrodes Precipitation of metals with changes in charge In principle, however, in the case of film formation on iron, reduction and precipitation of nickel dissolved (cathode reaction) due to iron dissolution (anode reaction) are slightly observed at the iron base. Precipitation throughout the entire film-forming period by the electrochemical reaction between electrodes. This precipitation reaction was not observed.

The characteristic of the film formation of this invention can be said to be the film obtained mainly by the electrochemical reaction between electrodes. That is, this film is obtained by obtaining electrochemical energy larger than the film obtained from an electroless process.

What follows is an embodiment of the present invention. The process of each Example and a comparative example is shown in Table 7.

The degreasing step is immersed for 4 to 5 minutes using an alkali degreasing agent of a predetermined concentration and temperature. Pickling process is immersed in 10% hydrochloric acid solution for 5-10 minutes. Surface adjustment is immersed in 0.2% PL-ZT manufactured by Nihon Parkerizing Co., Ltd. in Japan. The flushing process is carried out until the degreasing agent and other chemicals are completely removed from the object. Electrodeposition coating is made into 20-25 micrometers of coating thickness after baking using Power Top U-56 by NipponPaint of Japan.

Table 7 Process of Examples and Comparative Examples

( Process is indicated,-process not displayed)

fair Degreasing → Suse → Pickling → Suse → Surface adjustment → Phosphate Chemical Treatment → Suse → Process after chemical conversion Example 1 - - - Pure water washing → Electrodeposition coating → Pure water washing → Sobu (190 ℃, 25 minutes) Comparative Example 1 - - Example 2 - - Immersion in 5% sodium stearate solution (85 ° C, 5 minutes) → cold forging press Comparative Example 2 Example 3 - - - Pure water washing → Electrodeposition coating → Pure water washing → Sobu (190 ℃, 25 minutes) Comparative Example 3 - - - Example 4 - - - Pure water washing → Electrodeposition coating → Pure water washing → Sobu (190 ℃, 25 minutes) Example 5 - - -

Table 8 shows the composition and electrochemical conditions of the phosphate chemical treatment bath of each Example and the comparative example.

[Table 8] Composition and electrochemical conditions of phosphate chemical treatment bath

Treatment bath composition (g / l) Chemical Analysis of Treatment Bath Electrochemical Conditions of Treatment Bath Phosphate ions Nitrate Ion Nickel ion Zinc ion Sodium ions Pt Accelerator Concentration (Pt) pH ORP (mV) Ag / AgCl Electrode Potential EC (mS) Temperature (℃) Example 1 7.6 12 5.5 0.4 0 20 0 0.5 270 15.3 27.6 Comparative Example 1 7 20 0.5 3 6.4 12 5 3.05 520 - 28 Example 2 21.2 20.2 0.25 17.1 0 44 0 2.17 399 21 32.4 Comparative Example 2 Nihon Parker's Palbond 3500 bath, electroless treatment bath (80 ° C), immersed for 15 minutes 50 2.5 - - - 80 Example 3 4.3 17.1 6 0.8 0 28 0 1.2 275 20.9 30.4 Comparative Example 3 7 19 4.5 2.5 0.6 21 0 2.77 356 24.5 36.4 Example 4 2.8 10.1 3.8 0.4 0 18 0 2.09 338 9.1 28.7 Example 5 2.9 11 3.9 0.4 0 18 0 2.18 318 8.7 27.7

Table 9 shows the electrolytic treatment conditions of each Example and Comparative Example. Except for Comparative Example 2, the phosphate chemical treatment bath was filtered and circulated to prevent the treatment bath from being decomposed, and also to prevent turbidity due to sludge formation. The film of Comparative Example 2 is a thick film used for cold forging lubrication. The treatment bath was heated to 80 ° C. in order to obtain a thick film by electroless treatment.

Table 9 Electrolytic Treatment Conditions of Examples and Comparative Examples

Example 1

Automotive air conditioner parts (clutch, stator housing) shown in the drawing were used as the workpiece. The stator housing of FIG. 4 welds and joins the board (press punching part) used as the flat part 20, and the housing (press processed part) used as the outer peripheral part 21 in a painting evaluation test. The housing serving as the outer circumferential portion 21 is formed by pressing a flat plate into a structure having a fin. Therefore, the housing outer peripheral part is the surface which greatly deform | transformed by press work. The largely deformed surface is strongly adhered with lubricating oil at the time of press working. As a result, the surface is greatly deformed at the time of surface treatment, so that lubricating oil adheres to the surface. Therefore, this part tends to interfere with the reaction with respect to the surface treatment, thereby degrading the performance of the surface treatment. In the example of FIG. 4, coating corrosion resistance falls.

The treated material was subjected to phosphate chemical treatment under the process of Table 7 and the conditions of Tables 8 and 9. Further, the ORP indicated values in Table 8 are potentials (mV) expressed based on the Ag / AgCl electrode. When the displayed values based on the Ag / AgCl electrode are set to +210 mV, these values are converted to the hydrogen standard electrode potential.

Electrodeposition coating was carried out in the process after the chemical conversion treatment of Table 7. The coating corrosion resistance evaluation test was done about the electrodeposited coating object. The coating corrosion resistance evaluation test wound | wounded the coating film until it reached the base with a knife at the flat part and the outer peripheral part of a to-be-processed object, and was immersed in 5% sodium chloride solution at 55 degreeC for 240 hours. After washing for 24 hours, the treated object was washed with water, left to stand for 2 hours or more, and dried, and then the adhesive tape was strongly attached to the wound film surface with a knife. The coating corrosion resistance peeled off by tape peeling was measured, and paint corrosion resistance was evaluated. The smaller the peeling width, the better the corrosion resistance. The results of the evaluation of coating corrosion resistance are shown in Table 10 in comparison with Comparative Example 1.

Comparative Example 1

The same thing as Example 1 was used for the to-be-processed object. The process is the same as Example 1 except adding the surface adjustment process and performing the phosphate chemical conversion process by the electroless method. Phosphate chemical treatment was performed by phosphate chemical treatment using the electroless treatment using the methods shown in Tables 8 and 9. Evaluation of coating corrosion resistance was also performed by the same method as Example 1. The results of the coating corrosion resistance evaluation are shown in Table 10 in comparison with Example 1.

[Coating corrosion resistance evaluation result]

The results of the evaluation of coating corrosion resistance are shown in Table 10. As apparent from the comparison between Example 1 and Comparative Example 1, Example 1 had good corrosion resistance. Moreover, when the flat part and the outer peripheral part were compared, the flat part showed good corrosion resistance, but in Example 1, the difference was hardly observed. However, in Comparative Example 1, there is a large difference in corrosion resistance between the flat portion and the outer peripheral portion. This difference is because, as described above, in the electroless treatment, the influence of the press working that lowers the chemical conversion treatment of the metal surface appears. Since Example 1 is an example of the electrolytic treatment, a lot of electrochemical energy can be used for the electrolytic reaction. Therefore, since a phosphate chemical conversion film is formed without the influence of a press work, corrosion resistance is favorable.

[Table 10] Evaluation of Painting Corrosion Resistance

Peel width after salt immersion test (mm) Flat part Outer part Example 1 (electrolytic treatment) 0 1 or less Comparative Example 1 (Electroless Treatment) 5 Full surface peeling

[Interpretation of Formed Phosphate Chemically Treated Coating]

The analysis confirmed the difference in the film by the electrolytic treatment and the electroless treatment.

The phosphate chemical conversion coatings of Example 1 and Comparative Example 1 were analyzed by an energy dispersive X-ray analyzer (EDX) and a glow discharge analyzer (GDS). The analysis was divided into flat and outer periphery. The results are shown in Table 11.

[Table 11] List of Film Analysis Results (Cha Art)

Film Interpretation (EDX) Film Interpretation (GDS) Flat part Outer part Flat part Outer part Example 1 5 6 9 10 Comparative Example 1 7 8 11 Figure 12

First, the results of EDX were analyzed. EDX obtains information on the component elements of the film. The film was analyzed under the same conditions as shown in FIGS. 5 to 8.

Each EDX carart was compared with Example 1 (FIGS. 5 and 6) and Comparative Example 1 (FIGS. 7 and 8) in the same portion of the workpiece. The planar parts were compared. In FIG. 5 (electrolytic treatment), the nickel peak is higher than the zinc peak, while in FIG. 7 (electroless treatment), the zinc peak is higher than the nickel peak. And this tendency is also observed in the comparison of the outer circumference (FIGS. 6 and 8).

Table 12 shows the atomic number concentration analysis results of the film obtained from the EDX analysis results performed under the same conditions as shown in FIGS. 5 to 8. Atomic concentrations obtained from EDX analysis results include carbon (C) and gold (Au), but these are not coating components and are therefore omitted.

(Carbon is present because the film is washed with an organic solvent before analysis. Gold was used to fix the specimen to the analyzer.)

The ratio of the film component elements is calculated by calculating the atomic number concentration ratio of each element with respect to phosphorus (P) which is always contained in the phosphate film.

When examining the film, two parts can be considered as follows depending on the ratio of atomic number concentration of each metal element.

(1) Ratio of phosphorus (P) of metal (Ni) / phosphate which does not become phosphate

(2) The ratio of metal (Ni) that does not become a phosphate / metal and that becomes a phosphate (Fe)

[Table 12] Results of film analysis by energy dispersive X-ray analyzer (EDX)

Type of element Atomic number concentration (%) Atomic ratio ratio to P Atomic concentration ratio C O P Fe Ni Zn Au P O Fe Ni Zn Ni / Zn Ni / Fe Zn / Fe Example 1 Flat part 69.4 15.3 2.9 3.3 6.1 1.9 1.2 One 5.3 1.2 2.1 0.64 3.28 1.81 0.56 Outer part 65.6 16.7 3.2 5.3 6.1 1.8 1.4 One 5.3 1.7 1.9 0.56 3.39 1.15 0.34 Comparative Example 1 Flat part 61.6 17.9 3.8 10.4 0.04 4.7 1.5 One 4.7 2.7 0.01 1.24 0.008 0.004 0.46 Outer part 72.4 0.9 1.6 13.3 0.2 3.2 1.3 One 5.5 8.2 0.12 1.38 0.09 0.15 1.17 Example 2 76.6 11.7 3.1 0.96 - 5.5 2.1 One 3.8 0.3 - 1.76 0 - 5.68 Comparative Example 2 70.1 16.5 3.8 5.2 - 3.3 1.1 One 4.4 1.4 - 0.88 0 - 0.63

(1) Ratio of phosphorus (P) of metal (Ni) / phosphate which does not become phosphate

In the atomic number concentration ratio Ni / P, the concentrations of Ni in the planar portion and the outer circumferential portion of Example 1 were large as 2.1 and 1.9, but the concentrations of P in the planar portion and the outer circumferential portion of Comparative Example 1 were much larger as 0.01 and 0.12, respectively. . This indicates that the coating by electrolytic treatment contains a large amount of metal (Ni) that does not become a phosphate. On the other hand, in the case of electroless treatment, a film mainly composed of phosphate is formed, and the result of Comparative Example 1 proves this. From these results, it can be seen that a coating containing a large amount of metal (Ni) that does not form a phosphate is suitable for surface treatment coating and improves corrosion resistance.

Moreover, in the comparative example 1, the planar part contains more phosphorus than the outer peripheral part. The reason for this is that it is difficult to form a film on the outer circumference, and since the phosphate chemical film is not surely formed, this corresponds to a small amount of phosphate, which is the main component of the film.

(2) The ratio of metal (Ni) that does not become a phosphate / metal and that becomes a phosphate (Fe)

Fe is an element that functions as a base and forms a film together with phosphate crystals. If the film is reliably formed, the Ni / Fe ratio represents the ratio of Ni to Fe in the film, whereas if the film is not formed reliably, it represents the ratio of Ni to the base surface.

Although the Ni / Fe ratio of Example 1 is 1 or more with respect to both a planar part and an outer peripheral part, the Ni / Fe ratio in Comparative Example 1 is 1 or less with respect to both a flat part and an outer peripheral part. It can be seen from these results that the Ni content affects the paint corrosion resistance.

GDS analyzes the elements coming out of the film according to the glow discharge of the film. Information on the elements, film strength, and the like in the film can be obtained. For this reason, GDS provides information on (1) the distribution of elements in the coating and (2) the bond strength of the coating. The distribution of elements in the coating can be read directly from GDS chart art. Furthermore, "film strength" can be compared by the time it takes to reach the iron base when analyzed under the same conditions. In other words, the longer the time to reach the iron sheet, the stronger the coating.

Moreover, the voltage applied during GDS analysis depends on the type of element. For this reason, the analysis results of each film are not information on the "abundance ratio between elements in the film". However, in the analysis of Figs. 9 to 12, the analysis was performed under the same conditions. Therefore, the presence of an element in each film can be compared between each sample (film).

The GDS was used to compare Examples (FIGS. 9 and 10) and Comparative Examples (FIGS. 11 and 12) in the same portion of the workpiece.

First, (1) The distribution of elements in the film is compared.

By looking at the car arts of FIGS. 9 (electrolytic treatment) and 11 (electroless treatment) with respect to the planar portion, it is possible to analyze the manner in which nickel or the like is contained in the film. 9 (electrolytic treatment) shows that nickel is distributed throughout the film in the direction in which the film passes. 11 (electroless treatment) shows that nickel is hardly contained. 9 (electrolytic treatment) shows that iron atoms are slowly increasing in the coating, but the iron electrode (anode) used in the electrolytic treatment is dissolved to form a coating. Since the behavior of iron atoms is different from that of phosphorus (P), the phenomenon of binding of iron atoms to the coating can be predicted in the same manner as nickel. Moreover, this phenomenon also applies to the outer peripheral part.

Then, the bond strength of the film will be described. The film strength can be obtained by comparing the time (A) from the GDS analysis to the penetration of the film to the iron body. The results are shown in Table 13.

Table 13 Film Depth in GDS Analysis (Film Strength)

A: GDS analysis time (seconds) to reach iron Flat part Outer part Example 1 100 (Figure 9) 95 (Fig. 10) Comparative Example 1 25 (Figure 11) 30 (Figure 12)

In this evaluation, even if the chemical conversion treatment time in the film is almost the same, Example 1 has three times the strength of Comparative Example 1.

The above result supports that the phosphate chemical conversion coating containing the precipitation of the metal (Ni) with the change of the charge by the electrolytic treatment, which is a feature of the present invention, is effective for coating corrosion resistance as a function thereof.

Moreover, the nitrate concentration in the treatment bath of Example 1 is about 1/2 of the treatment bath of Comparative Example 1 as shown in Table 8. This is possible only by performing the electrolytic treatment in a bath containing no sodium ions. Since the nitric acid concentration is low, the present invention can be referred to as an environmentally friendly technology.

Example 2

As a to-be-processed object, the parts used for the automobile starter shown in FIG. 13 were used. This part (cylindrical part of 23 mm in diameter and 80 mm in length) is formed by cold forging pressing a spiral (spline shape) groove so as to engage with a tooth on the inner side of the pipe shape. The material is an alloy containing 1% of chromium. Phosphate conversion treatment is carried out in the form of cold forging press lubrication base. Therefore, the purpose of the phosphate chemical conversion coating is to lower the load during cold forging. Therefore, evaluation of a film is also performed based on the load at the time of cold forging.

The workpieces were subjected to electrolytic phosphate chemical treatment using the process of Table 7 and under the conditions of Tables 8 and 9. In the process after the chemical conversion in Table 7, sodium stearate is reacted with the phosphate chemically treated film to form a metallic soap (zinc stearate). Thereafter, cold forging press working is performed.

Comparative Example 2

The same thing as Example 2 was used for the to-be-processed object. The step is the same as that in Example 2 except that the phosphate chemical conversion treatment is different except for the surface adjustment step by pickling. Phosphate chemical conversion treatment was performed by electroless treatment (80 ° C.) by the method shown in Tables 8 and 9. Comparative Example 2 is a processing method currently in use.

[Evaluation of cold forging press working load, etc.]

Evaluation of cold forging press working load and coating analysis are summarized in Table 14.

"Cold forging press working load" of Table 14 is a load which a press receives in a cold forging press working. The lower the value of cold forging press working load, the better the lubrication performance. In addition, analysis of the film weight was performed by the following method.

A "water dissolved portion" is a product obtained by dipping a workpiece in water at 100 ° C. for 10 minutes and measuring the weight before and after the divided by the surface area of the workpiece.

"Metal soap powder" is a product obtained by dipping a to-be-processed object in 75 degreeC isopropyl alcohol (IPA) for 20 minutes, and measuring the weight before and after that, and dividing the weight obtained by the surface area of a to-be-processed object.

The "phosphate coating component" is obtained by dipping a treated object in 5% chromic acid (CrO ₃ ) at 50 to 70 ° C for 20 minutes, and dividing the weight obtained by measuring the weight before and after the surface area of the treated object.

Furthermore, Table 12 shows the analysis results of the atomic number concentration (%) by EDX.

[Table 14] Evaluation of cold forging press working load and coating analysis

Performance evaluation (cold forging press working load) Film analysis (EDX car art) Layer by layer and gravimetric analysis (g / m ² ) Water soluble Metal soap Phosphate Coating Composition Example 2 67 kg / cm ² (average value) 14 10.2 11.8 14.4 Comparative Example 2 82 kg / cm ² (average) Figure 15 2.4 1.8 6.7

In evaluation of cold forging press working load, Example 2 shows that it is superior to Comparative Example 2. The reason is evident from the "results of layering and gravimetric analysis" of Table 14. According to the "layers and weight analysis results" of Table 14, the film of Example 2 contained about 5 times as much metal soap powder as the film of Comparative Example 2. Metal soap powder contributes greatly to cold forging press lubrication. Therefore, it is clear that the cold forging press working load decreases as the content of the component increases.

Since metal soap powder is zinc stearate, it is necessary to contain a lot of zinc in a film. The amount of zinc in the film can be known from the result of EDX analysis. Comparing the car art of Fig. 14 and Fig. 15, it can be seen that Example 2 (Fig. 14), which is an electrolytic treatment film, contains less iron and contains more zinc. And this can be compared quantitatively in the atomic number concentration (%) analysis result of EDX of Table 12. If the chemical structure of the phosphate chemical conversion film is Zn ₃ (PO ₄ ) ₂ , the atomic number concentration ratio (Zn / P) of Zn to P is 1.5. In Table 12, when the atomic number concentration ratio of Zn / P is calculated, Example 2 becomes 1.76 and contains more Zn than Zn ₃ (PO ₄ ) ₂ , whereas Comparative Example 2 becomes 0.88, and the corresponding Zn ₃ It contains less zinc than (PO ₄ ) ₂ .

This indicates that the structure of the film can be changed by the electrolytic treatment. That is, the Zn ₃ (PO ₄ ) ₂ shows that the excess Zn is formed into a film in the form of zinc metal with the change of charge. This is finally possible by the electrolytic treatment of the present invention, and it contributes greatly to the reduction of cold forging press working load.

Moreover, the analysis result of Table 12 shows that the film of Example 2 is a film that does not completely contain Ni, which is a metal that does not form a phosphate. In addition, the electrolytic phosphate chemical treatment can be made to contain no metal which does not form a phosphate in this manner.

Example 3 and Comparative Example 3

Example 3 and Comparative Example 3 are for confirming the difference in the film formed by the electrolytic treatment.

The air conditioner parts for automobiles used in Example 1 and Comparative Example 1 were used as treated materials in Examples 3 and 3 and subjected to phosphate chemical treatment and electrodeposition coating according to the process shown in Table 7. Electrolytic phosphate chemical treatment was performed under the conditions shown in Tables 8 and 9. The main difference between Example 3 and Comparative Example 3 lies in the phosphate chemical treatment bath. The treatment bath of Example 3 does not contain Na ions, but the treatment bath of Comparative Example 3 contains Na ions. The coating corrosion resistance evaluation in Example 3 and Comparative Example 3 was performed in the same manner as in Example 1 and Comparative Example 1. These results are shown in Table 15.

[Table 15] Evaluation of Coating Corrosion Resistance (Maximum Peel Width)

Difference in treatment bath Peel width after salt immersion test (mm) Flat part Outer part Example 3 Na-ion free 0 5 Comparative Example 3 Contains Na ions One 10

The results of Table 15 show that Example 3 has better coating corrosion resistance than Comparative Example 3.

This difference is thought to be due to the difference in the phosphate chemical film formed. From Table 16, the result of the X-ray-diffraction pattern of the phosphate film of Example 3 and the comparative example 3 can be seen.

[Table 16] X-ray diffraction results of the film

Flat part Outer part Example 3 No peak of phosphate crystals (see Figure 16) No peak of phosphate crystals, Ni peak present (see FIG. 17) Comparative Example 3 A peak of phosphate crystals is present (see FIG. 18) A peak of phosphate crystals is present (see FIG. 19)

The difference regarding the phosphate chemical conversion film of Example 3 and the comparative example 3 is as follows.

(1) Presence or Absence of Phosphate Crystal Peaks

(2) presence or absence of Ni peaks

The results in Table 16 do not indicate that the film of Example 3 does not contain phosphate crystals, but indicates that the phosphate crystals are extremely fine, and that the composite of the Ni metal and the phosphate crystals is thereby progressing.

Table 17 summarizes the progress of the compounding of the Ni metal and the phosphate crystal in the film of Example 3.

[Table 17] Elemental analysis photo by EPMA (Electro Probe Micro Analysis) in film cross section direction

SEM photo (4000X) Elemental analysis pictures Phosphorus (P) Zinc (Zn) Nickel (Ni) Iron (Fe) Flat part Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Outer part Figure 25 Figure 26 Figure 27 Figure 28 Figure 29

The distribution of each element in the cross section of the film observed in the SEM photograph magnified at 4000 times in FIGS. 20 and 25 is shown in the analysis photograph (FIGS. 21 to 24 and 26 to 29) for each element. The results of these photographs show that each element has a uniform distribution in the film. From these photographs, it can be seen visually that the crystals are fine (results in Table 16) even if the film contains phosphate.

Moreover, these results correspond indirectly but with the results of the GDS analysis shown in Example 1 (Table 12, FIGS. 9 and 10).

From the results in Table 15, it can be seen that the film obtained from the treatment bath containing no Na ions of Example 3 in which the phosphate crystals were finely dispersed in Ni had an effective coating corrosion resistance.

Moreover, the X-ray diffraction pattern described in Japanese Patent No. 5-822481 is one example of the conventional electrolytic phosphate chemical conversion treatment, and shows all phosphate peaks.

Examples 4 and 5

Examples 4 and 5 are examples in which Ni is reliably formed in the presence of phosphate to reduce the amount of Fe electrolyzed to reduce the amount of Fe that is electrolytically deteriorated as much as possible. Therefore, only the electrolysis of Ni is performed in the first step of the cathode electrolytic treatment, followed by electrolysis of Ni and Fe simultaneously. At this time, the electrolytic amount of Fe is 1/3 to 1/8 less than that of Example 3.

The car air conditioner used in Example 3 was used as an object to be treated in Examples 4 and 5, followed by phosphate chemical treatment and electrodeposition coating according to the process of Table 6. Electrolytic phosphate chemical treatment was performed under the conditions of Tables 8 and 9.

The coating corrosion resistance evaluation of Examples 4 and 5 was performed by the same method as Example 1. These results are shown in Table 18.

[Table 18] Evaluation of Paint Corrosion Resistance (Maximum Peel Width)

Peel width after salt immersion test (mm) Flat part Outer part Example 4 0 2 Example 5 2 4

The paint corrosion resistance of Examples 4 and 5 is better than that of Comparative Example 3. As described in the description of Example 1, it is difficult to form a film on the outer peripheral part in the case of electroless treatment. When the electrolytic treatment of the present invention is carried out in Examples 4 and 5, it is possible to form a film on such a surface, indicating that corrosion resistance can be ensured.

Next, the EDX analysis result of the phosphate chemical conversion film obtained in Examples 4 and 5 is shown.

[Table 19] Results of film analysis by energy dispersive X-ray analyzer (EDX)

Type of element Atomic number concentration (%) Atomic ratio ratio to P Atomic concentration ratio P Fe Ni Zn P Fe Ni Zn Ni / Zn Ni / Fe Zn / Fe Example 4 Flat part 19 62.8 9.6 8.61 One 3.31 0.51 0.45 1.13 0.15 0.13 Outer part 9.7 77.7 7.3 5.3 One 8.01 0.75 0.55 1.36 0.09 0.07 Example 5 Flat part 19.9 51.9 15.4 12.9 One 2.61 0.77 0.64 1.20 0.30 0.24 Outer part 26.8 40 25.1 8.6 One 1.49 0.94 0.32 2.94 0.63 0.21

According to the result of Table 19, the tendency of the compound ratio of the element (Fe) which is not possessed does not change compared with Table 12. Ni and P are elements contained in the film, but their abundance ratio (Ni / P) is 0.5 or more in the results of Tables 12 and 18, indicating that Ni in the film is present in an amount of 1/4 or more than the amount of P. . These results show that the film obtained by the electroless treatment having a Ni / P ratio of less than 0.25 is significantly different (see Table 12).

The examples of Examples 4 and 5 show examples of cathode electrolysis using two Fe and Ni electrodes, and they also show that this method is effective.

The present inventors believe that if electrolytic treatment and electroless treatment at the time of "plating" are possible, practical electrolytic treatment in addition to the conventional electroless phosphate chemical treatment may be possible even in the case of phosphate chemical treatment, which is the same wet surface treatment as in the case of plating. In the end, the present invention was completed.

As described below, the concept of the present invention will be described.

(1) Each examination item of the electrolytic phosphate chemical treatment technique was determined by comparing and comparing the conventional wet electrolytic surface treatment technique with the electrolytic phosphate chemical treatment technique based on the conventional surface treatment technique.

(2) By investigating the preferred state of the electrolytic phosphate chemical treatment reaction, preferred treatment conditions were found within the investigated range.

(3) The film formed by the proposed electrolytic phosphate chemical treatment method was investigated.

[Existing Surface Treatment Technology]

Before describing the contents of the present invention, a conventional surface treatment technique is first described. The technique of the electrolytic phosphate chemical treatment method of the present invention was investigated by correlating such a conventional surface treatment technique with the electrolytic phosphate chemical treatment technique achieved.

Surface treatment techniques currently established practically, including the technique of the present invention, are classified as follows.

Surface treatment techniques are first classified into "dry surface treatment" and "wet surface treatment". Surface treatment techniques of this "wet surface treatment" are further classified into "electroless treatment" and "electrolytic treatment". Specific examples of the surface treatment of "electroless treatment" here include "electroless plating" and "electroless phosphate chemical treatment". Furthermore, specific examples of "electrolytic treatment" include "electroplating", "anode (anode) oxidation" and "electrodeposition", and the "electrolytic phosphate chemical treatment" of the present invention belongs to the category of "electroplating".

[Wet Surface Treatment (Review of Reaction Energy)]

As described above, wet surface treatments are classified into two types, "electroless treatment" and "electrolytic treatment".

The difference between "electroless treatment" and "electrolytic treatment" depends on the energy that promotes the reaction.

"Electroless treatment" depends on the chemical energy of the chemicals added to the treatment bath, such as reducing agents (plating) or oxidants (phosphate chemical treatment). In this regard, "electrolytic treatment" depends on electrical energy from an external power source.

Therefore, in the case of "plating", the baths required for "electroless plating" and "electroplating" are fundamentally different, and the baths required for "electroless plating" cannot be used for electrolytic treatment.

If this idea is applied to the phosphate chemical treatment method, the treatment in the "electroless treatment bath" and the "electrolytic treatment bath" should be fundamentally different.

[Electrolytic Treatment in Wet Surface Treatment]

1 shows a schematic diagram of the electrolytic treatment. This electrolytic treatment uses an external power source and consists of three components: the counter electrode, the solution and the workpiece in the electrolyzer.

The situation in which these three components are involved in the electrolytic reaction depends on the type of wet electrolytic treatment. It is summarized in Table 1 below.

[Table 1] Classification of Wet Electrolytic Treatment : Reacts, ×: does not react)

Counterplay solution Work piece (workpiece) Applied voltage level Existing technology Electroplating × × 10 V or more Anodic oxidation (aluminum material) × 10 V or more Electrodeposition coating × × 100 V or more Electrolytic Phosphate Chemical Treatment 1 to 50 V

The contents of Table 1 are described below.

In "electroplating", a plated coating component in the form of an anode (+ pole) (counter electrode) (for example, a zinc electrode in the case of zinc plating) is dissolved by application of voltage or current, and the dissolved plating coating component is a complex. The product is passed through the solution in a complex state and precipitated at the cathode (-pole). For this reason, the only component that reacts is the countercurrent component that dissolves. The object to be treated is a cathode, and there is no reaction such as dissolution in the electrolytic cell.

In "anode (anode) oxidation", the aluminum material in the form of an anode is dissolved in a treatment bath. At this time, the solvent (water) and the solute ions (anion) decompose as the voltage rises, and the oxygen ions generated by this decomposition. (O ^-2 ) and dissolved aluminum combine to form a film of aluminum oxide (Al ₂ O ₃ ) on the surface of the aluminum material. Materials that do not dissolve (react) during electrolysis are used for the counter electrode (cathode).

In "electrodeposition coating", a voltage is applied to colloidal organic matter and inorganic matter dispersed in water, electrolytic colloidal material is electrophoretic or precipitated, and then solidified on the surface of an electrode (a workpiece) to precipitate (coating film). Let's do it. That is, "electrodeposition" includes the electrolytic reaction of each component in a solution, and the only reactions due to voltage application are water in a solvent and colloidal material dispersed in water. The electrode (electrode or workpiece) does not dissolve or react.

Moreover, in "electrodeposition" it is important to maintain the solution state in a defined state (range).

If the solution state cannot be kept in a limited state due to the change (reaction) among the solution components due to solidification or decomposition, an effective electrodeposition coating film cannot be formed. Therefore, the electrodeposition coating bath is kept constant at a predetermined temperature to perform ultrafiltration treatment. Furthermore, the workpiece is washed with pure water prior to electrolysis so that unnecessary ions (such as Na ions) are not incorporated from the previous step before charging into the electrolyzer.

In contrast, the "electrolytic phosphate chemical treatment" of the present invention is completely different from the above-described three techniques in that all three components "large electrode", "solution" and "treatment" are dissolved and reacted. The reason is that in the prior art, such a difference was not recognized, and it was impossible to develop a technology that accommodates the difference. Therefore, it was difficult to practically apply such "electrolytic phosphate chemical treatment" in the prior art.

[Review items of electrolytic phosphate chemical treatment]

Table 2 shows a review item regarding the contents of various existing electrolytic treatment baths and phosphate chemical treatment baths when examining the "electrolytic phosphate chemical treatment" of the present invention.

[Table 2] Comparison of Properties of Electrolytic Treatment Baths

Electrolytic treatment Review item Reaction of each solution component to be a film Electrolytic tendency of the bath PH adjustment of bath The presence of unnecessary ions The presence of reaction promoters Weapon / Organic Classification Existing Electrolytic Treatment Electroplating none Medium (complex) none Yes (Na ⁺ ) none Inorganic ion reaction Anodic oxidation (aluminum material) Yes (solvent) Large (Strong Bath Bath) has exist none none Inorganic ion reaction Electrodeposition coating has exist Low (Electrolytic Bathing) has exist none none Organic matter reaction Phosphate Chemical Treatment Conventional electrolytic phosphate chemical treatment (prior art) has exist Low (with accelerator) has exist Yes (Na ⁺ ) has exist Inorganic ion reaction Electroless Phosphate Chemical Treatment (Reference) has exist Low (weak electrolyte bath) has exist Yes (Na ⁺ ) has exist Inorganic ion reaction Electrolytic Phosphate Chemical Treatment (Invention) has exist Medium (complex) has exist none none Inorganic ion reaction

In all of the items reviewed on the electrolytic reaction control which is shared by the existing electrolytic treatment forms of "electroplating", "anode oxidation", and "electrodeposition coating", the film is formed only on the surface of the electrolytically treated object in the electrolytic cell. As the reaction occurs, measures should be taken to prevent the reaction from occurring at other locations in the cell. That is, even if it is impossible to prevent a reaction similar to the film forming reaction from occurring at a position other than the surface of the workpiece in the electrolytic cell, measures should be taken so that the film formation takes place substantially by the electrolytic treatment on the surface of the workpiece.

In this regard, the respective items of review for each electrolytic treatment will be described below.

(1) "Electroplating" prevents the bonding of the dissolved metal ions in the electrolyzer even if it involves the process of dissolving the plated metal at the anode and then depositing at the cathode. Complexes are used as a means of preventing these bonds.

The treatment bath of "electroplating" is a complex bath of metal salts. This is because binding and precipitation of the metal ions in the solution (reaction between the solute components in the solution) are prevented, while the plated metal is dissolved from the electrode (anode) to precipitate at the cathode. Examples of known complexes are cyano (CN) complexes. Electroplating baths are usually not transparent and measures must be taken to ensure that the complex does not decompose in the treatment liquid even if it contains ions, such as Na ions, which are not involved in film formation. By taking these countermeasures, only a metal ion can be deposited on the surface of the cathode to form a plating film. (Na ions have different deposition potentials than plated metal ions and therefore do not precipitate at the cathode. This is consistent with electrochemical principles.)

(2) "Anode oxidation" includes electrolytic treatment using an object as an anode and an insoluble electrode as a cathode. At this time, the presence of ions not necessary for the film formation affects both the dissolution reaction and the oxidation (film formation) reaction of the material (for example, aluminum). This is because dissolved aluminum is extremely active in the treatment bath. The anode oxide film is formed by reaction of oxygen ions (O ^2- ) and dissolved aluminum ions produced by decomposition of a solvent in the form of water. In order to prevent dissolved aluminum ions from reacting with other ions, the incorporation of impurities in the treatment liquid should be extremely limited.

(3) "Deposition coating" includes the step of forming a coating film by electrolyzing one component in a solution on one electrode surface. Only solvents in the form of water and colloidal organics dispersed in water react by voltage application. A reaction involving the dissolution of the electrode (between the counter electrode and the workpiece) does not occur.

In the case of electrodeposition coating, it is important to maintain the solution state in a constant state (range) so as to form a good coating film. If a change (reaction) of each component occurs in the solution due to coagulation or decomposition, the electrodeposition coating cannot be formed effectively. For this reason, the electrodeposition coating bath is kept at a constant temperature at all times and the ultrafiltration treatment prevents the solidification of the colloidal components dispersed in the bath and maintains the dispersed state.

Further, in the electrodeposition coating bath, contamination by inhibitory ions such as Na ions is prevented as much as possible and maintained in a state close to pure water. This is because the presence of inhibitory ions inhibits the precipitation reaction on the electrode surface.

The above technical findings obtained from the prior art electrolytic treatment are summarized as follows.

In the case of the electrolytic treatment, it is necessary to prevent each component in the solution involved in the film formation from reacting except for the reaction on the electrode surface (interface).

(A) Prevention of mixing of impurities (anode oxidation, electrodeposition coating)

(B) Prevention of self-solidification of each component in solution by constant filtration, circulation and temperature maintenance (electrodeposition coating)

(C) use of complexes (electroplating)

It is thought that the "electrolytic phosphate chemical treatment method" in the present invention can be practically applied by reflecting the above-described technical findings of the method. The above conclusion, "In the case of electrolytic treatment, each component in the solution involved in the film formation must not react except the reaction on the electrode surface" is a concept common to all types of electrolytic surface treatment. to be. However, the specific measures to achieve this vary with each type of treatment.

The reason why the prior art, which is also a subject of the present invention, has not been able to attain the practical use of an efficient electrolytic phosphate chemical treatment method is to take a specific measure to prevent components in the solution involved in film formation from reacting at positions other than the electrode surface. It could not be found.

Electrolytic Phosphate Chemical Treatment Method of the Present Invention

Even if the electrolytic treatment is carried out, the "electrolytic phosphate chemical treatment method" of the present invention can be embodied so that the components in the solution involved in film formation do not substantially react at positions other than the electrode surface.

In order to achieve this, the present invention,

With at least phosphate,

At least the phosphate and phosphoric acid, the nitrate ion, the metal ion which forms a complex with the phosphate ion in the phosphate conversion treatment bath, and the dissolution of the ion dissolved in the phosphate conversion treatment bath to precipitate as a metal is an anode of the water type solvent. A phosphate chemical treatment bath containing a metal ion having an electrolytic reaction potential of -0.83 V (represented as a hydrogen standard electrode potential) is subjected to electrolytic treatment by contacting a workpiece to form a phosphate on the surface of the workpiece and to maintain conductivity. As a method of forming a film containing a metal material having

The phosphate chemical treatment bath has a concentration of 0 to 400 ppm of metal ions other than the coating component, and contains substantially no solids that affect the film forming reaction.

The potential to form a complex with phosphate ions in the phosphate chemical treatment bath, and the ions dissolved in the phosphate chemical treatment bath to be reduced and precipitated as a metal is -0.83 V Electrolytic treatment is carried out in a phosphate chemical conversion bath with a metallic material of more than (indicated by the hydrogen standard electrode potential).

In particular, in the present invention, the film forming reaction is minimized as much as possible except for the film formation in the bath, and the concentration of metal ions other than the film component in the phosphate conversion treatment bath is 0 to 400 ppm, By forming a phosphate chemical treatment bath that is substantially free of solids that affect the film-forming reaction and without the addition of an accelerator, the phosphate chemical treatment bath can be carried out smoothly and efficiently on the surface of the object to be treated.

In particular, in the present invention, the concentration of metal ions other than the coating components in the phosphate chemical treatment bath is set to 0 to 400 ppm, and the phosphate chemical treatment bath is made to substantially contain no solids that affect the film forming reaction. The film forming reaction can be carried out without depending mainly on the precipitation of the phosphate from the bath, so that a film containing at least a phosphate and a metal which does not form a phosphate on the surface of the workpiece can be provided.

In order to perform film formation efficiently, it is preferable to contain 1-100 ppm of metal ions in a phosphate conversion treatment bath other than the coating component which contains at least a phosphate.

As a preferable example of the specific composition of a phosphate chemical treatment bath, nitrate ion concentration 6-140 g / l, phosphate ion and phosphate concentration 0.5-60 g / l, the density | concentration of the metal ion which forms a complex with phosphate ion in the phosphate conversion treatment liquid 0.5 To 70 g / l and ions dissolved in the phosphate chemical treatment solution are reduced and precipitated as metals with metal ions having a potential of -0.83 V (denoted as hydrogen standard electrode potential), which is the anode electrolytic reaction potential of a solvent in water form. It contains concentration 0-40 g / l.

The phosphate chemical treatment method preferably does not use an acid having an acid dissociation degree greater than that of phosphate ions. An example of an acid having an acid dissociation degree greater than that of phosphate ions is nitric acid.

When an acid having an acid dissociation degree larger than phosphate ions is added to the treatment bath, the film forming reaction of phosphate on the surface of the workpiece is suppressed in the treatment bath, so that the reaction cannot be carried out efficiently.

As the metal ion forming a complex with the phosphate ion in the phosphate conversion treatment bath, at least one metal selected from the group consisting of zinc, iron, manganese and calcium is preferable.

Metal ions having a potential of reduced ions dissolved in the phosphate chemical treatment solution to be precipitated as metals above -0.83 V (represented as a hydrogen standard electrode potential), which is an anode electrolysis reaction potential of a water-type solvent, consist of nickel ions and copper ions. At least one metal ion selected from the group is preferred.

The present invention also provides an electrolytic treatment by contacting a conductive object with a conductive object in a phosphate chemical treatment bath containing at least phosphate ions and metal ions complexed with phosphate ions in the phosphate chemical treatment bath. In the electrolytic phosphate chemical treatment method comprising a method of forming a film containing at least phosphate on the surface of the object to be treated, the phosphate chemical treatment bath contains 0 to 400 ppm of metal ions other than the film component, and the film formation reaction The present invention provides an electrolytic phosphate chemical treatment method which contains substantially no solids affecting the phosphate chemical treatment treatment, and the object to be treated is electrolyzed in a phosphate chemical treatment bath between the metal material forming a complex with phosphate ions in the phosphate chemical treatment bath.

In the case of adopting this method, even if the formed film is mainly composed of a phosphate chemical film, 0 to 400 ppm of metal ions other than the coating component is contained in the phosphate chemical treatment bath, and the phosphate chemical treatment bath affects the film formation reaction. Since the itch does not substantially contain solid matter, the film forming reaction during phosphate chemical treatment can be efficiently carried out.

It is preferable that the concentration of metal ions other than the coating component containing at least phosphate in the phosphate chemical treatment bath is 0 to 100 ppm.

The phosphate chemical treatment bath has a concentration of 6 to 140 g / l for nitrate, 0.5 to 60 g / l for phosphate ions and phosphoric acid, and a concentration of 0.5 to 70 g / l for forming metal complexes with phosphate ions in the phosphate chemical treatment solution. Is preferably.

The phosphate chemical treatment bath preferably does not contain an acid having an acid dissociation degree greater than that of phosphate ions.

In this case, an example of an acid having an acid dissociation degree greater than that of phosphate ions is nitric acid.

Since the phosphate chemical treatment bath does not contain an acid having a higher acid dissociation degree than the acid dissociation degree of phosphate ions, the film formation can be efficiently performed for the same reason as described above.

Furthermore, at least one metal ion selected from the group consisting of zinc ions, iron ions, manganese ions, and calcium ions is preferable as the metal ions complexed with the phosphate ions in the phosphate chemical treatment solution.

The electrolytic treatment using the to-be-processed object as an anode may be performed by the phosphate chemical treatment method, and the electrolytic treatment using the to-be-processed object as a cathode may be performed by the phosphate chemical treatment method.

After the electrolytic treatment using the workpiece as an anode, the electrolytic treatment using the workpiece as a cathode may be performed by a phosphate chemical treatment method.

As a result of performing such an electrolytic treatment, the film formation reaction can be performed on the surface of a to-be-processed object, after etching the surface of a to-be-processed object and exposing a fresh surface. Thus, a film having improved adhesion to the surface of the workpiece can be obtained.

Cathodic electrolytic treatment in which the treated material in the phosphate chemical treatment method is used as a cathode is insoluble in the same metal material and / or phosphate chemical treatment bath as the metal in which ions dissolved in the phosphate chemical treatment bath are reduced and precipitated. An electrolytic phosphate chemical treatment method comprising at least one of an electrolytic treatment using a phosphorus conductive material for an anode or an electrolytic treatment using a metal material forming a complex in a phosphate chemical treatment bath for an anode is preferable.

As a result of using such a treatment method, by appropriately adjusting the component ratio between the phosphate forming film and the metal which does not form phosphate, it is possible to form a film having required properties on the surface of the object to be treated.

Cathodic electrolytic treatment in which the treated material in the phosphate chemical treatment method is used as a cathode is insoluble in the same metal material and / or phosphate chemical treatment bath as the metal in which ions dissolved in the phosphate chemical treatment bath are reduced and precipitated. The electrolytic treatment is carried out using a phosphorus conductive material for the anode, and the electrolytic treatment is performed using a metal material forming a complex in the phosphate chemical treatment bath for the anode as one cycle, and the cycle is at least one cycle. The electrolytic phosphate chemical treatment method which is performed once is preferable.

As a result of using this treatment method, a thick film having the required properties as described above can be formed.

The cathode electrolytic treatment, in which the treated material in the phosphate chemical treatment method is used as a cathode, is subjected to electrolytic treatment in the same metal material and / or phosphate chemical treatment bath in which ions dissolved in the phosphate chemical treatment bath are reduced and precipitated. Electrolytic phosphate chemical treatment method in which electrolytic treatment is performed by using an insoluble conductive material as an anode and performing electrolytic treatment using an electrolytic cell for electrolytic treatment and a metal material forming a complex in the phosphate chemical treatment bath as an anode. This is preferred.

As a result of using such a treatment method, a separate electrolytic cell is used, so that the precipitation reaction of each component can be controlled independently, thereby making it easier to form a film having required properties.

Furthermore, at least one metal selected from the group consisting of nickel and copper is preferable as the metal material which is the metal which is reduced and precipitated by the metal dissolved in the phosphate conversion treatment bath.

As the metal material forming the complex in the phosphate conversion treatment bath, at least one metal selected from the group consisting of zinc, iron, manganese and calcium is preferable.

If the object is not in contact with the phosphate chemical treatment bath, the metal material used as the anode is used as a cathode during the electrolytic treatment in which the object is used for the cathode, and a material insoluble in the phosphate chemical treatment bath is used as the anode. It is preferable to apply a voltage of 5 V or less between the anode and the cathode.

If the object is not in contact with the phosphate chemical treatment bath, the cathode uses a metal material used as an anode during the electrolytic treatment in which the object is used for the cathode, and a material insoluble in the phosphate chemical treatment bath as an anode. It is preferred to apply a voltage between the anode and the cathode that does not substantially dissolve the cathode.

In this way, by taking countermeasures against the case where the object is not in contact with the phosphate chemical treatment bath, dissolution of the metal material can be suppressed when the object is not treated.

It is preferable to remove a portion of the phosphate chemical treatment bath from a bath tank having a phosphate chemical treatment bath to circulate into the bath after thermodynamically stabilizing the energy state of a portion of the liquid of the phosphate chemical treatment bath.

It is preferable to remove a part of the phosphate chemical treatment bath from the bath having the phosphate chemical treatment bath, and also to remove the solids precipitated during the phosphate chemical treatment during the film forming reaction, and then circulate it to the bathtub.

By using this method, nitrides (e.g., NO ₂ ) and inevitably generated reaction products (sludge) generated by reduction of nitrate ions in addition to the surface of an object to be processed, for example, by electrolytic reaction, can be removed from the treatment bath. Therefore, excessive reactions other than the film formation reaction can be suppressed in the treatment bath.

When each component of the phosphate chemical treatment bath is newly replenished, a part of the phosphate chemical treatment bath is removed, and a supplement solution containing a component of the treatment bath having a concentration higher than the concentration of at least one component among the components constituting the phosphate chemical treatment bath, It is preferred to add to the removed bath.

According to this method, the treatment bath can be easily replenished.

Dissolve the ions in the phosphate conversion bath to precipitate as metal, dissolving a metal with a potential above -0.83 V (represented as the hydrogen standard potential) in the phosphate conversion treatment bath A reaction of reducing from a cationic state by electrolytic treatment to precipitate on the surface of a workpiece, and a metal ions forming a complex with phosphate ions in a phosphate chemical treatment bath to precipitate as phosphate crystals upon dehydrogenation of phosphate ions; The present invention provides an electrolytic phosphate chemical treatment method in which an object to be treated is used as a cathode for electrolytic treatment.

According to this treatment method, since two different reactions can be simultaneously performed in a treatment bath, a desired composite film can be formed on the surface of the workpiece.

Furthermore, the metal ion which forms a complex with a phosphate ion is preferably at least one metal selected from the group consisting of Fe, Zn, Mn, Ca and Mg.

Metals having a potential of reduced ions dissolved in the phosphate conversion bath to be precipitated as metals above -0.83 V (represented as a hydrogen standard potential), which is an anode of a water-type solvent, are represented by Ni, Cu, Fe, and Zn. Preference is given to at least one metal selected from the group above.

The composition of the treatment bath in the case of performing the electrolytic treatment is such that the ratio of the concentration (g / l) of the phosphate ion and the metal ion forming a complex to the concentration (g / l) of phosphate ions and phosphoric acid is 0.1 or more. It is preferable.

By the phosphate ions and the concentration of phosphate (g / l) the ratio of phosphate ions and a complexing metal ion concentration (g / l) in forming the about 0.1 or more, more preferably 0.25 or more phosphoric acid (H ₃ PO ₄ ) May be present in the treatment bath in the form of phosphate ions (H ₂ PO ₄ ⁻ ) to inhibit oxidation of phosphate ions on the cathode surface. Moreover, this makes it possible to control the phosphoric acid present in the treatment bath.

In the electrolytic phosphate chemical conversion treatment in which an object to be treated is used as a cathode and subjected to electrolytic treatment, it is preferable to change the voltage applied between the anode and the metal material forming the cathode.

Furthermore, it is preferable that the change of applied voltage at the start of electrolytic treatment is in the form of a pulse. By using this method, even if the film starts to be formed only at a specific position of the workpiece in the initial film formation step on the surface of the workpiece, the film formation position can be forcibly changed whenever the electrolytic treatment voltage changes. Therefore, a film can be formed uniformly on the surface of a to-be-processed object.

The present invention provides a composite coating comprising a phosphate compound and a metal that does not form a phosphate on a steel surface, wherein the metal and phosphate compound forming the coating are dispersed throughout the coating.

The present invention provides a composite coating comprising a phosphate compound and a metal that does not form a phosphate on a steel surface, wherein the metal that does not form a phosphate is present at least on the outermost surface of the coating.

The present invention provides a composite film of a phosphate compound and a metal that does not form a phosphate on a steel surface, wherein the film does not exhibit peaks other than phosphate peaks in X-ray diffraction analysis.

The present invention provides a composite film of a phosphate compound and a metal which does not form a phosphate on a steel surface, wherein the composite film having at least 0.25 of the number of phosphorus atoms constituting the phosphate crystal has an atomic number of a metal that does not form a phosphate. .

As a metal which does not form a phosphate, at least 1 sort (s) of metal chosen from the group which consists of Ni, Cu, Fe, and Zn is preferable.

Furthermore, as the metal forming the phosphate compound, at least one metal selected from the group consisting of Fe, Zn, Mn, Ca and Mg is preferable.

When the total steel is 100% by weight, the steel preferably contains at least 95% by weight of iron (Fe).

X-ray diffraction analysis is preferably performed by ESCA or EDX analysis.

Compared with the conventional treatment bath, the electrolytic phosphate chemical treatment bath of the present invention has a higher electrolytic tendency, and thus has a high concentration of film-forming metal ions, a low pH, and a low concentration of a substance not involved in the reaction. It is possible to provide a phosphate chemical conversion treatment technique that is more suitable for electrolytic treatment than the conventional technique, because it is possible to secure the transparency of the treatment bath that does not require removal and does not generate sludge.

Claims (39)

With at least phosphate, Anode electrolysis of a solvent in the form of water in which the phosphate ion and the phosphoric acid, the nitrate ion, the metal ion forming a complex with the phosphate ion in the phosphate conversion treatment bath, and the ion dissolved in the phosphate conversion treatment bath are reduced to precipitate as a metal A conductive metal that does not form phosphate on the surface of the object by electrolytic treatment by contacting the object with a phosphate chemical treatment bath containing a metal ion having a reaction potential of -0.83 V (represented as a hydrogen standard electrode potential). An electrolytic phosphate chemical treatment method for forming a film containing a material, The phosphate chemical treatment bath has a concentration of 400 ppm or less of metal ions other than the coating component, and does not contain a solid that affects the film forming reaction. The potential to form a complex with the phosphate ions in the phosphate conversion treatment bath, and the ions dissolved in the phosphate conversion treatment bath to be reduced as a metal is the anode electrolysis reaction potential of the solvent in water form -0.83. An electrolytic phosphate chemical treatment method comprising electrolytic treatment in a phosphate chemical treatment bath with a metallic material of V (indicated by hydrogen standard electrode potential). The electrolytic phosphate chemical treatment method according to claim 1, wherein the phosphate chemical treatment bath contains 100 ppm or less of metal ions other than the components of the film containing at least phosphate. The phosphate chemical treatment bath according to claim 1, wherein the phosphate chemical treatment bath has a concentration of 6 to 140 g / l, a phosphate ion and a phosphoric acid concentration of 0.5 to 60 g / l, and a concentration of metal ions forming a complex with phosphoric acid in the phosphate chemical treatment solution. To 70 g / l and ions dissolved in the phosphate chemical treatment solution are reduced and precipitated as metals with metal ions having a potential of -0.83 V (denoted as hydrogen standard electrode potential), which is the anode electrolytic reaction potential of a solvent in water form. An electrolytic phosphate chemical treatment method comprising a concentration of 40 g / l or less. 4. The electrolytic phosphate chemical treatment method according to claim 3, wherein the phosphate chemical treatment bath does not contain an acid having an acid dissociation degree greater than that of the phosphate ion. The electrolytic phosphate chemical treatment method according to claim 1, wherein the metal ion which forms a complex with the phosphate ion in the phosphate chemical treatment bath is one selected from the group consisting of zinc, iron, manganese and calcium. . 2. The metal ions of claim 1, wherein the ions dissolved in the phosphate chemical treatment solution are reduced and precipitated as metals with a metal ion of -0.83 V (denoted as a hydrogen standard electrode potential) equal to or greater than the anode electrolysis reaction potential of the solvent. Electrolytic phosphate chemical treatment method, characterized in that one kind selected from the group consisting of. In the phosphate conversion treatment bath containing phosphate ions and metal ions forming complexes with phosphate ions in the phosphate conversion treatment bath, a conductive object is brought into contact with each other to perform electrolytic treatment. In the electrolytic phosphate chemical treatment method for forming a film containing phosphate on the surface of water, the phosphate chemical treatment bath contains 400 ppm or less of metal ions other than the components of the film, and contains a solid that affects the film forming reaction. And electrolytically treating the phosphate chemical treatment with a metal material which forms a complex with phosphate ions in the phosphate chemical treatment bath. 8. The electrolytic phosphate chemical treatment method according to claim 7, wherein the phosphate chemical treatment bath contains 100 ppm or less of metal ions other than the component forming the film containing phosphate. 8. The phosphate chemical treatment bath according to claim 7, wherein the phosphate chemical treatment bath has a concentration of 6 to 140 g / l, a phosphate ion and a phosphoric acid concentration of 0.5 to 60 g / l, and a metal ion complexed with phosphoric acid in the phosphate chemical treatment solution. An electrolytic phosphate chemical treatment method comprising a concentration of 0.5 to 70 g / l. The electrolytic phosphate chemical treatment method according to claim 7, wherein the phosphate chemical treatment bath does not contain an acid having an acid dissociation degree greater than that of the phosphate ions. The electrolytic phosphate chemical treatment method according to claim 10, wherein an acid having an acid dissociation degree greater than that of the phosphate ions in the phosphate chemical treatment bath is nitric acid. 8. The electrolytic phosphate chemical composition according to claim 7, wherein said metal ion which forms a complex with said phosphate ion in said phosphate conversion treatment bath is one metal selected from the group consisting of zinc, iron, manganese and calcium. Treatment method. The electrolytic phosphate chemical treatment method according to claim 1 or 7, wherein the treated object is used as an anode for electrolytic treatment. The electrolytic phosphate chemical treatment method according to claim 1 or 7, wherein the treated object is used as a cathode for electrolytic treatment. The electrolytic phosphate chemical treatment method according to claim 1 or 7, wherein the electrolytic treatment is carried out using the workpiece as an anode and then electrolytic treatment using the workpiece as a cathode. 8. The cathode electrolytic treatment according to claim 1 or 7, wherein the electrolytic treatment of the phosphate chemical treatment method using the object to be treated as a cathode is the same as a metal in which ions dissolved in the phosphate chemical treatment bath are reduced and precipitated. Electrolytic treatment using a metal material or a conductive material insoluble in the phosphate chemical treatment bath as an anode, and electrolytic treatment using a metal material forming a complex in the phosphate chemical treatment bath as an anode. Electrolytic phosphate chemical treatment method. The method of claim 1, wherein the cathode electrolytic treatment of the phosphate chemical treatment method in which electrolysis is carried out using the object to be treated as an anode is performed by the same metal material as the metal from which ions dissolved in the phosphate chemical treatment bath are reduced and precipitated. The electrolytic treatment using an insoluble conductive material as an anode in the phosphate conversion treatment bath is followed by an electrolysis treatment using a metal material forming a complex in the phosphate conversion treatment bath as an anode. Electrolytic phosphate chemical treatment method characterized in that carried out one or more times. The cathode electrolytic treatment of the phosphate chemical treatment method in which electrolysis is carried out using the object to be treated as an anode, wherein the electrolytic material is insoluble in a phosphate chemical treatment bath as an anode. An electrolytic phosphate chemical treatment method characterized by separating an electrolytic cell and a metal material forming a complex in the phosphate chemical treatment bath into an electrolytic cell for electrolysis using an anode. 19. The metal material as claimed in any one of claims 17 to 18, wherein the same metal material as the metal dissolved, reduced and precipitated in the phosphate conversion treatment bath is one metal selected from the group consisting of nickel and copper. Electrolytic phosphate chemical treatment method. 19. The metal material according to any one of claims 16 to 18, wherein the metal material forming a complex in the phosphate conversion treatment bath is one metal selected from the group consisting of zinc, iron, manganese and calcium. Electrolytic phosphate chemical treatment method. The metal material used as an anode in the electrolytic treatment using the to-be-processed material as a cathode when the to-be-processed material is not in contact with the said phosphate conversion bath, And a material insoluble in the phosphate chemical treatment bath as an anode, and applying a voltage of 5 V or less between the anode and the cathode. The metal material used as an anode in the electrolytic treatment using the to-be-processed material as a cathode when the to-be-processed material is not in contact with the said phosphate conversion bath, And using a material insoluble in the phosphate chemical treatment bath as an anode, and applying a voltage between the anode and the cathode such that the cathode does not dissolve. The tank according to claim 1 or 7, wherein the tank is removed from the tank having the phosphate chemical treatment bath to thermodynamically stabilize the energy state of a part of the liquid in the phosphate chemical treatment bath. The electrolytic phosphate chemical treatment method characterized by sending back. 24. The method of claim 23, wherein a portion of the phosphate chemical treatment bath is removed from the tank having the phosphate chemical treatment bath, and the solids precipitated in the phosphate chemical treatment bath are separated and returned to the tank during the film forming reaction. Electrolytic phosphate chemical treatment method. 24. The method of claim 23, wherein when replenishing the components of the phosphate chemical treatment bath, a portion of the phosphate chemical treatment bath is removed and the concentration is higher than the concentration of one of the components constituting the phosphate chemical treatment bath. A replenishment liquid containing process bath components is added to said removed bath. In the electrolytic phosphate chemical treatment method using an object as a cathode for electrolytic treatment, the potential at which metal ions dissolved in the phosphate chemical treatment bath is reduced to precipitate as a metal is an anode electrolytic reaction potential of a water-type solvent. A reaction in which a metal at least -0.83 V (denoted as a hydrogen standard electrode potential) is dissolved in a phosphate chemical treatment bath, reduced from a cationic state by electrolytic treatment, and precipitated on the surface of the object to be treated; phosphoric acid in the phosphate chemical treatment bath An electrolytic phosphate chemical treatment method comprising a reaction in which a metal ion forming a complex with an ion precipitates as a phosphate crystal in the phosphate chemical treatment bath in response to a dehydrogenation reaction of the phosphate ion. 27. The electrolytic phosphate chemical treatment method according to claim 26, wherein the metal ion forming a complex with the phosphate ion is one metal selected from the group consisting of Fe, Zn, Mn, Ca and Mg. 27. The metal according to claim 26, wherein the potential of the metal ions dissolved in the phosphate conversion bath is reduced and precipitated as a metal is equal to or greater than -0.83 V (denoted as a hydrogen standard electrode potential) which is an anode electrolysis reaction potential of a solvent in water form. An electrolytic phosphate chemical conversion treatment method, characterized by one kind of metal selected from the group consisting of Ni, Cu, Fe, and Zn. 27. The composition of any one of claims 1, 7, and 26, wherein the composition of the treatment bath to be subjected to the electrolytic treatment forms a complex with phosphate ions with respect to the concentration of phosphate ions and phosphoric acid (g / l). Electrolytic phosphate chemical conversion treatment method characterized in that the ratio of the metal ion concentration (g / l) to 0.1 or more. 27. An electrolytic phosphate chemical treatment method in which an electrolytic treatment is carried out using a to-be-processed object as a cathode as described in any one of claims 1, 7, and 26, wherein an anode and a cathode are formed at the start of the electrolytic treatment. An electrolytic phosphate chemical conversion treatment method comprising changing a voltage applied between a metal material to be formed. The electrolytic phosphate chemical treatment method according to claim 30, wherein the voltage change applied at the start of the electrolytic treatment is in the form of a pulse. A composite film on a steel surface, comprising a metal that does not form a phosphate and a phosphate compound, wherein the metal and the phosphate compound constituting the film are dispersed throughout the film. A composite film of a steel surface, comprising a metal which does not form a phosphate and a phosphate compound, and wherein metal is present on the outermost surface of the film which does not form a phosphate. A composite film of a steel surface, comprising a metal that does not form a phosphate and a phosphate compound, and the film does not exhibit any peak other than the phosphate peak in X-ray diffraction analysis. A composite film on a steel surface, comprising a metal that does not form a phosphate and a phosphate compound, wherein the number of atoms of the metal that does not form a phosphate is 0.25 or more of the number of phosphorus atoms constituting the phosphate crystal. 36. The composite film according to any one of claims 32 to 35, wherein the metal that does not form a phosphate is one metal selected from the group consisting of Ni, Cu, Fe, and Zn. The composite coating according to any one of claims 32 to 35, wherein the metal that does not form a phosphate compound is one metal selected from the group consisting of Fe, Zn, Mn, Ca, and Mg. The composite film according to any one of claims 32 to 35, wherein when the total amount of steel is 100% by weight, the steel contains 95% by weight or more of iron (Fe). The composite film according to claim 34, wherein the X-ray diffraction analysis is performed by ESCA or EDX analysis.