JP2005023422A - Metal surface treatment method and surface-treated metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal surface treatment method capable of imparting excellent corrosion resistance and capable of forming an excellently corrosion-resistant film on a metallic substrate such as iron, zinc, aluminum, or magnesium and to provide a surface-treated metal treated thereby. <P>SOLUTION: The metal surface treatment method comprises the step of forming a chemically converted film on the surface of a metallic substrate by a chemical conversion treatment with a chemical converting agent containing a zirconium-containing compound and a fluorine-containing compound. The chemical conversion treatment is performed by cathodic electrolysis treatment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a metal surface treatment method and a surface-treated metal.

The surface of the metal material is usually subjected to a surface treatment for the purpose of improving properties such as corrosion resistance. As one type of such surface treatment, a surface treatment with a chemical conversion treatment agent containing a zirconium compound is known. Such a surface treatment method is performed by an electroless reaction. The treatment metal elutes by the treatment liquid, fluoride is produced by the reaction of the eluting metal ions with fluorine ions, and the hydrogen ions. Zirconium hydroxide / fluoride and treatment by generation of hydrogen by reduction, and fluoride ions are replaced by hydroxide ions by hydrolysis of zircon complex ions, and the pH increases near the surface of the treatment object. An insoluble zirconium salt made of metal fluoride and a metal salt of the object to be treated are deposited on the metal surface.

In such an electroless reaction of the zirconium chemical conversion treatment agent, it is extremely difficult to generate a uniform reaction on the entire surface of the object to be treated, and thus it is difficult to form a sufficiently dense and uniform film. , It becomes a film containing a lot of oxides and fluorides by etching the material, and the corrosion resistance deteriorates. In addition, in the electroless reaction, since the anode and cathode reactions are performed on the same surface, if a chemical conversion film is formed, the reactivity becomes low, so only a rough thin chemical conversion film such as a material metal or an alkali metal can be obtained. It is difficult to obtain a uniform and dense protective film.

In this way, the chemical conversion coating obtained by the electroless reaction using the zirconium chemical conversion treatment agent is particularly suitable for an object to be treated such as an iron-based substrate or a zinc-based substrate that has low reactivity with the chemical conversion treatment agent. It was difficult to provide sufficient rust prevention. Moreover, also in the surface treatment of an aluminum-type base material and a magnesium-type base material, it is requested | required to achieve the corrosion resistance in a higher level by forming the chemical conversion film which has a further favorable property. For this reason, the metal surface treatment method which can form a more uniform and precise chemical conversion treatment film is calculated | required.

As a metal surface treatment method, a surface treatment method by an electrolytic reaction is known. (For example, refer to Patent Documents 1 and 2.) However, these relate to a phosphate compound or a titanium-based treatment method, and are not for forming a uniform and dense zirconium chemical conversion treatment film. In particular, the chemical conversion treatment method using a phosphate compound has a problem of giving a load to the environment due to eutrophication. Moreover, it reacts with metal ions in the phosphating bath to generate sludge. Furthermore, the chemical conversion treatment with a titanium compound cannot achieve a sufficiently high level of corrosion resistance.

Further, Patent Document 3 contains (A) a compound containing at least one of Ti, Zr, Hf and Si, (B) a fluorine-containing compound as a supply source of HF, The ratio K = A / B of the total molar weight A of the metal elements Ti, Zr, Hf and Si to the molar weight B when all fluorine atoms in the fluorine-containing compound of the component (B) are converted to HF is 0. A surface treatment composition in the range of 0.06 ≦ K ≦ 0.18 and a metal surface treatment method for contacting the metal surface with the composition are disclosed.

However, here, when chemical conversion treatment is performed by electrolytic treatment using a composition for surface treatment in which a compound containing fluorine and zirconium is dissolved, a large amount of excess fluorine and alkali metals exist in the solution. Even if an electrolytic voltage is applied to the treatment material, the cathode protection effect is difficult to obtain, and a chemical conversion film containing a relatively large amount of fluoride and alkali metal compound is formed, so that the corrosion resistance cannot be sufficiently satisfied. Moreover, the corrosion problem of the equipment by a large amount of fluorine also occurs.

JP 2000-234200 A JP 2002-194589 A International Publication No. 02/103080 Pamphlet

In view of the above, the present invention is a metal surface treatment method that can form a film having excellent corrosion resistance and excellent corrosion resistance on a metal substrate such as iron, zinc, aluminum, and magnesium, and a surface-treated metal treated thereby. Is intended to provide.

The present invention is a metal surface treatment method comprising a step of forming a chemical conversion film on the surface of a metal workpiece by a chemical conversion treatment reaction with a chemical conversion treatment agent containing a zirconium-containing compound and a fluorine-containing compound. It is a metal surface treatment method characterized by performing by electrolytic treatment.

In the cathode electrolytic treatment, the concentration of the zirconium-containing compound in the chemical conversion treatment agent is 10 to 100000 ppm in terms of zirconium metal, and the ratio of the mass of all zirconium metal to the mass of total fluorine (zirconium content / fluorine content) is 0.2. It is preferable that the pH is adjusted to 1 to 6 and adjusted to 1 to 1.0.

The cathode electrolytic treatment, the voltage 0.1～40V, is preferably carried out under conditions of a current density 0.1~30A / dm ^2.
The metal workpiece is preferably at least one selected from the group consisting of an aluminum-based substrate, a zinc-based substrate, an iron-based substrate, and a magnesium-based substrate.

The present invention is also a surface-treated metal having a chemical conversion coating obtained by the above-described metal surface treatment method.
Hereinafter, the present invention will be described in detail.

In the metal surface treatment method of the present invention, a chemical conversion film is formed by cathodic electrolytic treatment of a metal surface with a chemical conversion treatment agent containing a zirconium-containing compound and a fluorine-containing compound. When reacted by cathodic electrolysis, the film becomes denser and more uniform than the chemical conversion film by electroless treatment. For this reason, even if the amount of the formed film is the same as the chemical conversion treatment film by electroless treatment, a chemical conversion treatment film excellent in corrosion resistance is formed.

When an electrolytic reaction is performed with a chemical conversion treatment agent containing a zirconium-containing compound and a fluorine-containing compound, an anticorrosive chemical conversion film having extremely excellent corrosion resistance is obtained, and obtained by an electrolytic reaction of a titanium-based or phosphate-based chemical conversion treatment agent. Corrosion resistance superior to that of the obtained chemical conversion film can be obtained. For this reason, use in a wide range is expected and preferable.

When a chemical conversion treatment agent containing a zirconium-containing compound and a fluorine-containing compound is used and a chemical conversion film is to be formed on an aluminum-based substrate by electroless treatment, first, as shown in the following reaction formulas (1) and (2) Etching of a raw material occurs, and subsequently, a zirconium-based chemical conversion film is formed mainly by hydrolysis of fluorozirconium as shown in the following reaction formulas (3) to (5).

That is, in the case of forming a film by electroless treatment, a chemical conversion film is formed by the occurrence of the reaction formulas (1) to (5), so that a zirconium-based chemical conversion film containing a relatively large amount of fluorine is formed. As a result, a film having poor corrosion resistance is formed. On the other hand, when a chemical conversion treatment agent containing a zirconium-containing compound and a fluorine-containing compound is subjected to cathode electrolytic treatment, a hydrogen generation reaction mainly occurs on the metal surface, and the material metal is cathodic protected, so that it is not etched and covered. There is no generation of fluoride in the treated metal. Accordingly, in the vicinity of the metal surface, deposition of a relatively stable zirconium oxide film occurs due to hydrolysis of zirconium complex ions, and a dense and stable protective film having a low fluorine content is formed. In addition, when the chemical conversion treatment agent is used and a chemical conversion coating is formed on an iron-based or zinc-based substrate by cathodic electrolysis, a coating with a reduced amount of fluorine can be formed, thereby improving the corrosion resistance. It is assumed that it can be done.

Moreover, when surface-treating an aluminum-based substrate, aluminum ions are usually accumulated in the equilibrium bath composition. In this case, in the electroless treatment, if 500 ppm or more of aluminum is accumulated, the chemical conversion reactivity is hindered, and thus treatment such as water supply and disposal is required. On the other hand, cathodic electrolytic treatment forms a film with a relatively small amount of aluminum ion etching (the film conversion efficiency is good), and has little influence on the accumulated aluminum ions, so that unnecessary water supply and disposal are not required. .

The zirconium-containing compound is not particularly limited as long as it is a compound containing zirconium, and examples thereof include fluorozirconic acid or its lithium, sodium, potassium, ammonium salt, zirconium fluoride, and zirconium oxide. These may be used alone or in combination of two or more.

The fluorine-containing compound is not particularly limited as long as it is a fluorine-containing compound. Besides the above-mentioned zirconium fluoride, etc., hydrofluoric acid, ammonium fluoride, ammonium hydrofluoride, sodium fluoride, fluoride A sodium hydrate etc. can be mentioned. These may be used alone or in combination of two or more.

In the metal surface treatment method of the present invention, the cathode electrolytic treatment is carried out in such a manner that the concentration of the zirconium-containing compound in the chemical conversion treatment agent is 10 ppm as the lower limit in terms of zirconium metal, 100000 ppm as the upper limit. It is preferable that (zirconium content / fluorine content) be adjusted so that the lower limit is 0.2, the upper limit is 1.0, and the pH is lower limit 1 and the upper limit is 6. By performing the cathode electrolytic treatment with such adjustment, a chemical conversion film having a relatively small fluorine content can be formed, so that the corrosion resistance can be further improved.

In the cathode electrolytic treatment, as a method for adjusting the concentration of the zirconium-containing compound and the amount of zirconium / fluorine to the specified range, for example, the total zirconium concentration in the chemical conversion treatment agent is determined by using an atomic absorption analyzer. Can be adjusted by supplying the zirconium-containing compound and the fluorine-containing compound into the treatment bath while measuring using an ion chromatograph. Moreover, as a method of adjusting the said pH to the said regulation range, it can adjust, for example by supplying nitric acid or ammonium hydroxide in a processing bath, measuring using a pH meter.

In the cathode electrolytic treatment in the present invention, the chemical conversion treatment agent in the treatment bath is preferably adjusted such that the concentration of the zirconium-containing compound is within a range of a lower limit of 10 ppm and an upper limit of 100,000 ppm in terms of zirconium metal. If it is less than 10 ppm, the zirconium compound does not sufficiently precipitate on the metal surface, and thus the corrosion resistance may not be improved. Moreover, when it mixes exceeding 100,000 ppm, the effect beyond it cannot be expected and it is uneconomical. The lower limit is more preferably 30 ppm, and the upper limit is more preferably 5000 ppm.

In the cathode electrolytic treatment in the present invention, the chemical conversion treatment agent in the treatment bath is composed of the mass as total zirconium metal (total mass of all zirconium as zirconium metal contained in the chemical conversion treatment agent) and the mass of total fluorine (chemical conversion treatment). The ratio (zirconium amount / fluorine amount) to the total mass of all fluorine contained in the agent is preferably adjusted to a lower limit of 0.2 and an upper limit of 1.0. If it is less than 0.2, the amount of fluorine becomes excessive, and the formation of a chemical conversion film by the cathode electrolytic treatment may be hindered. Moreover, since a chemical conversion film having a relatively large amount of fluorine is formed, the corrosion resistance may be inferior. If it exceeds 1.0, the amount of total fluorine becomes insufficient, and precipitation of the metal salt may occur. The lower limit is more preferably 0.25, and the upper limit is more preferably 0.8.

In the cathode electrolytic treatment in the present invention, the chemical conversion treatment agent in the treatment bath is preferably adjusted to have a pH within a range of a lower limit of 1 and an upper limit of 6. If the pH is less than 1, the zirconium compound is difficult to precipitate, so that a sufficient amount of film cannot be obtained, and the corrosion resistance may be lowered. A pH exceeding 6 is not preferable because a sufficient amount of film cannot be obtained. The lower limit is preferably 2, and the upper limit is more preferably 5.

In addition to the above components, the chemical conversion treatment agent includes metal ions such as titanium, manganese, silicon, zinc, cerium, iron, molybdenum, vanadium, trivalent chromium, and magnesium; tannic acid, imidazoles, triazines, triazoles, Other rust inhibitors such as guanines, hydrazines, biguanides, phenol resins, silane coupling agents, colloidal silica, amines, phosphoric acid; surfactants; chelating agents; may contain resins, etc. .

In the metal surface treatment method of the present invention, the cathode electrolytic treatment is an electrolytic treatment using an object to be treated as a cathode.

The cathode electrolysis treatment preferably has a voltage of a lower limit of 0.1V and an upper limit of 40V. If it is less than 0.1 V, the amount of the coating is reduced and the corrosion resistance may be reduced. If it exceeds 40 V, the effect of increasing the coating amount is saturated, which may be disadvantageous in terms of energy. The lower limit is more preferably 1V, and the upper limit is more preferably 30V.

The cathode electrolytic treatment preferably has a current of a lower limit of 0.1 A / dm ² and an upper limit of 30 A / dm ² . If it is less than 0.1 A / dm ² , the amount of the coating is reduced and the corrosion resistance may be reduced. If it exceeds 30 A / dm ² , the effect of increasing the coating amount is saturated, which may be disadvantageous in terms of energy. The lower limit is more preferably 0.2 A / dm ² and the upper limit is more preferably 10 A / dm ² .

The treatment time of the cathode electrolytic treatment is preferably a lower limit of 3 seconds and an upper limit of 180 seconds. If it is less than 3 seconds, the formation of a film is small and the corrosion resistance is deteriorated. If it exceeds 180 seconds, the effect of increasing the coating amount is saturated, which may be disadvantageous in terms of energy.

The cathode electrolysis treatment temperature is preferably a lower limit of 10 ° C. and an upper limit of 70 ° C. When it is less than 10 ° C., the formation of a film is small and the corrosion resistance is deteriorated. If it exceeds 70 ° C., the effect of increasing the coating amount is saturated, which may be disadvantageous in terms of energy. The lower limit of the treatment temperature is not particularly controlled, and the treatment can be performed at room temperature.

In the cathode electrolytic treatment, the electrode used as a counter electrode is not particularly limited as long as it is an electrode that does not dissolve in the chemical conversion treatment agent. For example, stainless steel, platinum-plated titanium, niobium-plated titanium, carbon, iron, nickel, zinc, etc. Can be mentioned.

Examples of the workpiece to which the metal surface treatment method of the present invention can be applied include iron-based substrates, aluminum-based substrates, zinc-based substrates, and magnesium-based substrates. Iron, aluminum, zinc-based substrate, magnesium-based substrate is an iron-based substrate whose substrate is made of iron and / or an alloy thereof, an aluminum-based substrate whose substrate is made of aluminum and / or an alloy thereof, and a substrate Means a zinc-based substrate made of zinc and / or an alloy thereof, and a magnesium-based substrate made of magnesium and / or an alloy thereof. In particular, since zirconium-based chemical conversion treatment agents cannot provide sufficient corrosion resistance, phosphate-based chemical conversion treatment agents have been generally used for iron-based and zinc-based bases. A chemical conversion film having sufficient corrosion resistance can be formed. For this reason, it is applicable also to the objective of dephosphorylating the chemical conversion treatment agent of an iron base and a zinc base. The metal surface treatment method of the present invention is applied to a chemical conversion treatment of an object to be processed consisting of a plurality of metal substrates among an iron-based substrate, an aluminum-based substrate, a zinc-based substrate, and a magnesium-based substrate. Thus, excellent corrosion resistance can be imparted to each workpiece.

It does not specifically limit as said iron-type base material, For example, a cold-rolled steel plate, a hot-rolled steel plate, etc. can be mentioned. It does not specifically limit as said aluminum-type base material, For example, 5000 series aluminum alloy, 6000 series aluminum alloy, etc. can be mentioned.

The zinc-based substrate is not particularly limited. For example, galvanized steel sheet, zinc-nickel plated steel sheet, zinc-iron plated steel sheet, zinc-chromium plated steel sheet, zinc-aluminum plated steel sheet, zinc-titanium plated steel sheet, zinc- Examples thereof include zinc-based electroplating such as magnesium-plated steel sheet and zinc-manganese-plated steel sheet, zinc such as hot-dip plating and vapor-deposited steel sheet, or zinc-based alloy-plated steel sheet.

It does not specifically limit as said magnesium-type base material, For example, the magnesium metal and magnesium alloy which are produced by rolling, die-casting method, thixo molding method, etc. can be mentioned. It does not specifically limit as said magnesium alloy, For example, AZ31, AZ91, AZ91D, AM60, AM50, AZ31B etc. can be mentioned. By using the metal surface treatment method, it is possible to simultaneously subject the iron, aluminum, zinc and magnesium base materials to chemical conversion treatment.

The amount of zirconium in the chemical conversion film formed by the metal surface treatment method is preferably a lower limit of 10 mg / m ² and an upper limit of 300 mg / m ² . Thereby, the outstanding corrosion resistance can be provided. If it is less than 10 mg / m ² , the corrosion resistance may not be sufficient. Even if it exceeds 300 mg / m < ² >, the improvement of an effect is not seen but there exists a possibility that it may not be economical. The lower limit is more preferably 20 mg / m ² , and the upper limit is more preferably 150 mg / m ² .

The surface of the metal substrate is preferably subjected to degreasing treatment, post-degreasing water washing treatment, pickling treatment, pickling water washing treatment, and the like before the cathode electrolytic treatment with the chemical conversion treatment agent.

The degreasing treatment is performed to remove oil and dirt adhering to the surface of the base material, and usually with a degreasing agent such as phosphorus-free and nitrogen-free degreasing cleaning liquid at about 30 to 55 ° C. for about several minutes. Immersion treatment is performed. If desired, a preliminary degreasing process can be performed before the degreasing process.

The post-degreasing rinsing treatment is performed by spraying once or more with a large amount of rinsing water in order to wash the degreasing agent after the degreasing treatment.

As the pickling treatment, an immersion treatment is usually performed at a temperature of 30 to 60 ° C. for several minutes with an acid detergent such as sulfuric acid containing an oxidizing agent or a mixed pickling solution of sulfuric acid and nitric acid. The water washing treatment after the pickling can be performed by a conventionally known method. Moreover, you may perform a water washing process after a cathode electrolytic process.

This invention is also a surface treatment metal which has a chemical conversion treatment film obtained by the said metal surface treatment method. The surface-treated metal of the present invention is excellent in corrosion resistance when a corrosion-resistant primer coating such as cationic electrodeposition coating, powder coating, and thermosetting resin is further formed on the chemical conversion film. The coating that can be performed on the surface-treated metal of the present invention is not particularly limited, and examples thereof include cationic electrodeposition coating, powder coating, and roll coating. The cationic electrodeposition coating is not particularly limited, and a conventionally known cationic electrodeposition coating made of an aminated epoxy resin, an aminated acrylic resin, a sulfoniumated epoxy resin, or the like can be applied.

Since the metal surface treatment method of the present invention is a method of forming a chemical conversion film by subjecting a chemical conversion treatment agent containing a zirconium-containing compound and a fluorine-containing compound to cathode electrolytic treatment, a treatment material having excellent corrosion resistance can be obtained. . In addition, it can impart excellent corrosion resistance to all of iron, zinc, aluminum, and magnesium-based substrates, and is not a method that uses metals such as hexavalent chromium. .

In particular, the concentration of the zirconium-containing compound in the chemical conversion treatment agent is 10 to 100000 ppm in terms of zirconium metal, and the ratio of the mass of all zirconium metal to the mass of total fluorine (zirconium content / fluorine content) is 0.2 to 1.0. When the pH is adjusted to 1 to 6 and the cathode electrolytic treatment is performed, a chemical conversion film having a relatively small fluorine content is formed, so that the corrosion resistance can be further improved.

The chemical conversion treatment agent used in the present invention can provide excellent corrosion resistance even without containing phosphate ions, and therefore does not cause environmental problems such as eutrophication and suppresses the amount of sludge. It is also a method that can be done.

Since the metal surface treatment method of the present invention has the above-described configuration, it is more resistant to corrosion than when performing electroless treatment or performing electrolytic treatment using a titanium-based or phosphoric acid-based treatment agent. Can be improved. In addition, because it is a method that can give excellent corrosion resistance to all materials of iron-based substrate, aluminum-based substrate, zinc-based substrate or magnesium-based substrate, such as automobile bodies and parts , An iron-based substrate, an aluminum-based substrate, a zinc-based substrate, and a magnesium-based substrate. In addition, the load on the environment is small and the generation of sludge is suppressed.

EXAMPLES Hereinafter, although an Example is hung up and demonstrated in more detail, this invention is not limited only to these Examples. In the examples, “parts” and “%” mean “parts by mass” and “% by mass” unless otherwise specified.

Examples 1-13, Comparative Examples 1-7
Preparation of chemical conversion treatment agent Zirconic hydrofluoric acid, zircon ammonium fluoride, fluorinated titanic acid, phytic acid, aluminum nitrate, hydrofluoric acid, phosphoric acid, water-soluble phenol, tannic acid Then, ion exchange water was added to prepare a chemical conversion treatment agent as shown in Table 1.

Preparation of test plate 70 mm × 150 mm × 0.8 mm A1100 (manufactured by Nippon Test Panel) was degreased by immersion for 30 seconds at 70 ° C. using a 3% aqueous solution of an alkaline degreasing agent (Surf Cleaner 322N8, Nippon Paint). . After spraying with tap water for 30 seconds and washing with water, a pickling treatment agent (NP Conditioner 2000, Nippon Paint) 25% aqueous solution was used for immersion at 70 ° C. for 30 seconds for pickling. It was washed with tap water for 30 seconds. Next, the prepared chemical conversion treatment agent was subjected to cathode electrolytic treatment under the conditions shown in Table 1 using SUS304 as a counter electrode. The amount of zirconium in the coating (mg / m ² ) and the mass ratio of F / Zr in the coating were analyzed using “XRF1700” (Shimadzu X-ray fluorescence analyzer).

In the cathode electrolytic treatment, the concentration of the chemical conversion treatment agent in the treatment bath as zirconium metal, the mass ratio of zirconium / fluorine, and the pH were adjusted to the values shown in Table 1 as follows. .
The total zirconium concentration in the chemical conversion treatment agent in the treatment bath was measured using an atomic absorption spectrometer NOVAA330 manufactured by Rigaku, and the total fluorine concentration was measured using an ion chromatograph DX-120 manufactured by Nippon Dionex Co., Ltd. The acid was adjusted by replenishing the treatment bath. Moreover, the pH of the chemical conversion treatment agent in the treatment bath was adjusted by supplying nitric acid or ammonium hydroxide to the treatment bath while measuring using a pH meter D-24 manufactured by Horiba.

Evaluation of physical properties of test plate The corrosion resistance of the test plate was evaluated by the following evaluation method.
<Corrosion resistance>
Based on JIS Z 2371, a 5% salt spray test (2000 hours) was conducted, and the rust generation rate of the treated plate was examined after the test. The rust generation area on the surface of the treated plate was visually evaluated according to the following evaluation criteria.
10: No white rust generation 9: White rust generation area less than 10% 8: Less than 20% 7: Less than 30% 6: Less than 40% 5: Less than 50% 4: Less than 60% 3: 3: 70 Less than% 2: Less than 80% 1: Less than 90%

From Table 1, those obtained by electroless treatment (Comparative Examples 1 to 5) were inferior in corrosion resistance compared to those obtained by cathode electrolysis treatment (Examples). As a result, it has been clarified that the corrosion resistance can be improved by performing a cathode electrolytic treatment to form a film. Further, when fluorinated titanic acid was used (Comparative Example 6), the corrosion resistance was inferior compared to when a chemical conversion treating agent containing zirconium was used.

Examples 14-21, Comparative Examples 8-11
Preparation of chemical conversion treatment agent Zircon hydrofluoric acid as the zirconium-containing compound and fluorine-containing compound, nitrate as the other metal-containing compound, and ion-exchanged water were added to obtain a chemical conversion treatment agent as shown in Table 2. Prepared.

Preparation of test plate 70 mm × 150 mm × 0.8 mm SPCC-SD (manufactured by Nippon Test Panel), 70 mm × 150 mm × 0.8 mm galvanized steel sheet (GA steel sheet, manufactured by Nippon Test Panel), 70 mm × 150 mm × 0 .8 mm 5182 series aluminum (manufactured by Nippon Test Panel) was degreased by spraying at 40 ° C. for 2 minutes using a 2% aqueous solution of an alkaline degreasing agent (Surf Cleaner 53, Nippon Paint). After spraying with tap water for 30 seconds and washing with water, the prepared chemical conversion agent was subjected to cathodic electrolysis under the conditions shown in Table 2 using SUS304 as the counter electrode. Subsequently, after spraying with tap water for 30 seconds and washing with water, spraying with pure water for 30 seconds and washing with water. Next, using electrodeposition Powernix 110 (Nippon Paint's electrodeposition paint), electrodeposition is applied to a dry film thickness of 20 μm, and after washing with water, baking is performed by heating at 170 ° C. for 20 minutes to prepare a test plate. did.

The total zirconium concentration in the chemical conversion treatment agent in the treatment bath was measured using an atomic absorption spectrometer NOVAA330 manufactured by Rigaku, and the total fluorine concentration was measured using an ion chromatograph DX-120 manufactured by Nippon Dionex Co., Ltd. By adjusting the acid to the treatment bath, the values shown in Table 2 were adjusted. In addition, the pH of the chemical conversion treatment agent in the treatment bath was measured by using a pH meter D-24 manufactured by Horiba, Ltd., and nitric acid or ammonium hydroxide was replenished in the treatment bath. It adjusted so that it might become.

Comparative Example 12
Preparation of test plate SPCC-SD of 70 mm × 150 mm × 0.8 mm was degreased by spray treatment at 40 ° C. for 2 minutes using a 2% aqueous solution of an alkaline degreasing agent (Surf Cleaner 53, manufactured by Nippon Paint). After spraying with tap water for 30 seconds and washing with water, the surface is adjusted for 30 seconds at normal temperature using Surffine 5N-8M (surface adjuster manufactured by Nippon Paint Co., Ltd.), SurfDyne SD6350 (Zinc Phosphate manufactured by Nippon Paint Co., Ltd.) The treatment agent was subjected to cathode electrolytic treatment under the conditions shown in Table 2 using SUS304 as a counter electrode. Subsequently, after spraying with tap water for 30 seconds and washing with water, spraying with pure water for 30 seconds and washing with water. Next, using electrodeposition Powernix 110 (Nippon Paint's electrodeposition paint), electrodeposition is applied to a dry film thickness of 20 μm, and after washing with water, baking is performed by heating at 170 ° C. for 20 minutes to prepare a test plate. did.

Comparative Example 13
A test plate was prepared in the same manner as in Comparative Example 12 except that the electroless treatment was performed instead of the cathode electrolytic treatment.

Evaluation of physical properties of test plate The secondary adhesion of the test plate was evaluated by the following evaluation method.
<Secondary adhesion test (SDT)>
Two vertical and parallel cuts reaching the substrate were put in the obtained test plate, and then immersed in a 5% NaCl aqueous solution at 50 ° C. for 480 hours. Thereafter, the cut part was peeled off with tape, and the peeling of the paint was observed. The evaluation results are shown in Table 2.
○: Peel width less than 3 mm ×: Peel width of 3 mm or more

<Sludge>
After treating 1 m ² of cold rolled steel sheet (SPCC-SD), galvanized steel sheet and 5182 series aluminum per liter of chemical conversion treatment agent, the turbidity in the chemical conversion treatment agent was visually observed.
○: No turbidity ×: Turbidity

From Table 2, those obtained by electroless treatment (Comparative Examples 8 to 13) had lower secondary adhesion than those obtained by cathode electrolytic treatment (Examples 14 to 21). As a result, it has been clarified that the secondary adhesion can be improved by performing a cathode electrolytic treatment to form a film. Moreover, in Examples 14 to 18, the generation of sludge was suppressed as compared with the case where the electrolytic treatment was performed with the zinc phosphate treating agent (Comparative Example 12) and the case where the electroless treatment was performed (Comparative Example 13).

Examples 22-23
Preparation of chemical conversion treatment agent Zirconic hydrofluoric acid, ammonium zircon fluoride, and γ-aminopropyl triethoxysilane were added as the zirconium-containing compound and fluorine-containing compound, and ion-exchanged water was added, as shown in Table 3. A chemical conversion treatment agent was prepared.

Preparation of test plate 70 mm x 150 mm x 2.0 mm thixomolding magnesium alloy AZ91D using a 1% aqueous solution of alkaline degreasing agent (Surf Magine SF120 Cleaner, Nippon Paint) for 2 minutes at 50 ° C for degreasing did. After spraying with tap water for 30 seconds and washing with water, the pickling agent (Surf Magdyne SF400, manufactured by Nippon Paint) 1% aqueous solution was used for spraying at 50 ° C. for 2 minutes for pickling. After spraying with tap water for 30 seconds and washing with water, the desmutting agent (Surf Magine SF300, manufactured by Nippon Paint) 10% aqueous solution was used for spraying at 60 ° C. for 5 minutes for pickling. After spraying with tap water for 30 seconds and washing with water, the prepared chemical conversion treatment agent was subjected to cathodic electrolysis using SUS304 as a counter electrode under the conditions shown in Table 3. Subsequently, after spraying with tap water for 30 seconds and washing with water, spraying with pure water for 30 seconds and washing with water.

The total zirconium concentration in the chemical conversion treatment agent in the treatment bath was measured using an atomic absorption spectrometer NOVAA330 manufactured by Rigaku, and the total fluorine concentration was measured using an ion chromatograph DX-120 manufactured by Nippon Dionex Co., Ltd. By adjusting the acid to the treatment bath, the values shown in Table 3 were adjusted. Further, the pH of the chemical conversion treatment agent in the treatment bath was measured using a pH meter D-24 manufactured by HORIBA, Ltd., and nitric acid or ammonium hydroxide was replenished in the treatment bath to obtain the values shown in Table 3. It adjusted so that it might become.

Comparative Example 14
Instead of chemical conversion treatment by cathodic electrolytic treatment, a commercially available manganese phosphate treating agent SF572 (manufactured by Nippon Paint Co., Ltd.) was used in the same manner as in Example 22 except that the immersion treatment was performed at 50 ° C. for 2 minutes. A test plate was prepared.

Comparative Example 15
Instead of chemical conversion treatment by cathodic electrolytic treatment, a commercial 5% aqueous solution of zirconium phosphate treatment agent Alsurf 440 (manufactured by Nippon Paint Co., Ltd.) was used, and the immersion treatment was carried out at 50 ° C. for 2 minutes, as in Example 22. A test plate was prepared.

The test plates obtained in Examples 22 to 23 and Comparative Examples 14 to 15 were evaluated for corrosion resistance as follows.
In the evaluation in Example 1, the corrosion resistance was evaluated in the same manner as the evaluation in Example 1 except that the evaluation time of <corrosion resistance> was 2000 hours instead of 2000 hours.

From Table 3, as compared with Comparative Examples 14 and 15, the test plates obtained in Examples 22 to 23 were excellent in corrosion resistance.

The metal surface treatment method of the present invention can be suitably applied to objects to be treated such as iron-based substrates, zinc-based substrates, aluminum-based substrates, and magnesium-based substrates.

Claims (5)

A metal surface treatment method comprising a step of forming a chemical conversion film on the surface of a metal object by a chemical conversion treatment with a chemical conversion treatment agent containing a zirconium-containing compound and a fluorine-containing compound,
The chemical conversion treatment reaction is performed by cathode electrolytic treatment. In the cathode electrolysis treatment, the concentration of the zirconium-containing compound in the chemical conversion treatment agent is 10 to 100,000 ppm in terms of zirconium metal, and the ratio of the mass of all zirconium metal to the mass of total fluorine (zirconium amount / fluorine amount) is 0.2 to 0.2. The metal surface treatment method according to claim 1, wherein the method is performed by adjusting the pH to 1.0 to 1-6. The cathode electrolytic treatment, the voltage 0.1～40V, current density 0.1~30A / dm those in which claim 1 or 2 metal surface treatment method according performed under the conditions of ^2. The metal surface treatment method according to claim 1, 2 or 3, wherein the metal workpiece is at least one selected from the group consisting of an aluminum base, a zinc base, an iron base and a magnesium base. . A surface-treated metal comprising a chemical conversion treatment film obtained by the metal surface treatment method according to claim 1, 2, 3 or 4.