JP2010116588A - Treatment liquid for surface conditioning for metal phosphate film chemical conversion treatment, method for producing metal with phosphate film formed by using the same, and method for forming phosphate film on metal surface - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for forming a sufficiently fine and dense phosphate film onto the inner sheet part of a metal component having a bag structure, particularly to the part, where the bag structure is narrow and the stirring of a treatment liquid is inferior. <P>SOLUTION: The treatment liquid for surface conditioning for metal phosphate film chemical conversion treatment, in which zinc phosphate fine particles are dispersed into water, contains zinc by 10 to 2,000 ppm as a soluble component, and has the pH of 4 to 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a phosphate coating chemical conversion treatment applied to the surface of a metal material such as steel, galvanized steel sheet, and aluminum. The chemical conversion reaction is accelerated and shortened before the chemical conversion treatment, and the phosphate coating crystal is formed. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface conditioning treatment liquid used for miniaturization, a method for producing a metal having a phosphate coating formed thereon, and a method for forming a phosphate coating on a metal surface, and particularly a bag structure The present invention relates to a technique for generating a sufficiently fine phosphate coating up to the inside of a metal structure having s.

In recent years, in automobile phosphate treatment, it is required to form fine and dense phosphate-coated crystals on a metal surface in order to improve corrosion resistance after painting. Therefore, in order to activate the metal surface in order to obtain fine and dense phosphate-coated crystals, and to create nuclei for the precipitation of phosphate-coated crystals, a surface conditioning process is performed before the phosphate film conversion treatment process. It has been adopted. The following is an example of a general phosphate coating forming process that is performed to obtain fine and dense phosphate coating crystals.
(1) Degreasing (2) Washing with water (multistage)
(3) Surface adjustment (4) Phosphate coating conversion treatment (5) Water washing (multistage)
(6) Pure water washing

  The surface conditioning step is used to make the phosphate coating crystal fine and dense. Regarding the composition, what is called “Jurnsted salt” composed of titanium, pyrophosphate ion, orthophosphate ion, sodium ion and the like as main components has been used (Patent Documents 1 to 3).

  Recently, a surface conditioner using fine zinc phosphate particles has been used to further improve the surface conditioning effect and make the phosphate coating crystals finer and denser. It became possible to form a dense film on the part (Patent Documents 4 and 5).

  However, many parts of automobiles have a bag-like structure composed of two or more plates such as doors. Inside these bag structures, the circulation of the treatment liquid is poor during the phosphate coating conversion treatment, and stirring is carried out. Is processed without being fully performed. As a result, with the plate inside the bag structure (hereinafter, the inside of the bag structure is referred to as the inner plate portion and the portion exposed to the outside is referred to as the outer plate portion), it is difficult to form a normal phosphate coating and is not sufficiently covered with the coating. In other words, the material is partially exposed to a so-called formation failure state. It is clear that sufficient corrosion resistance cannot be obtained even if the phosphate coating in such a state is coated. Therefore, it is necessary to generate a sufficient phosphate coating on such an inner plate portion.

As a means to solve this, most of the techniques have so far been mainly equipment-related means for promoting the circulation of the liquid into the bag structure, and these require large costs such as equipment modification. (Patent Documents 6 and 7). In addition, depending on the type of bag structure, sufficient liquid circulation may not be expected.
U.S. Pat. No. 2,874,081 U.S. Pat. No. 2,322,349 US Pat. No. 2,310,239 Japanese Patent Laid-Open No. 10-245685 JP 2004-68149 A JP-A-9-279361 JP-A-11-33477 JP2003-27252 JP 2006-299379 A

  In the above prior art, a sufficiently fine and dense phosphate coating can be formed on the inner plate portion of the metal structure having a bag structure, particularly on the site where the bag structure is narrow and the processing liquid is not stirred well. There wasn't.

  As a result of examining the reason why a sufficiently dense coating is not formed on the inner plate part as compared with the outer plate part, the present inventors have found that a soluble zinc component (typically, a constituent component of the phosphate chemical conversion treatment liquid) It was discovered that zinc ions) are greatly related to the ease of formation of phosphate coatings. (Hereinafter, the term “chemical conversion” will be used. “Chemical conversion” is a term that indicates how easily a phosphate coating film can be formed regardless of some difference in reactivity such as the surface of the material.) If the amount of the soluble zinc component (typically zinc ions) in the phosphate chemical conversion treatment solution is large, the chemical conversion is good and the condition of forming the phosphate coating on the inner plate portion is improved. However, it is known that the performance such as the corrosion resistance of the phosphate coating deteriorates when the amount of the soluble zinc component (typically zinc ions) in the treatment liquid is large.

  For this reason, as a result of various investigations, the soluble zinc component (typically zinc ions) in the treatment liquid is generated along with the formation of the phosphate film, particularly in a narrow bag structure, when the treatment liquid is in an unstirred state. As a result, it was found that the chemical conversion property deteriorates because the soluble zinc component (typically zinc ions) is not sufficiently supplied to the interface of the workpiece. That is, FIG. 1 shows the simulated metal structure used in the embodiment of the present invention, but the opening is only a small hole in this way, and the treatment liquid is confined inside this structure during the phosphate treatment. It becomes. In this process, when the chemical conversion reaction proceeds and a phosphate coating starts to form, soluble zinc components (typically zinc ions) are consumed and reduced as coating components, but the openings are small and soluble zinc components from the outside. Since (typically, zinc ions) do not diffuse, it has been clarified that zinc becomes insufficient and chemical conversion becomes worse. It was also found that the film formation at the early stage of the chemical conversion reaction has a great influence on the chemical conversion. From this, a soluble zinc component (typically a water-soluble zinc salt serving as a zinc ion source) was added to the surface conditioner to increase the zinc concentration at the workpiece interface and improve the chemical conversion. It is.

  The surface conditioner contains water-insoluble zinc phosphate fine particles to promote nucleation, and these fine particles are adsorbed on the surface of the object to be processed, and phosphate-coated crystals grow as crystal nuclei. . The application of this principle is the conventional surface conditioning technology.

  The inventors consider that the soluble zinc component concentration (typically the zinc ion concentration) of the treatment liquid at the workpiece interface is important in order for the adsorbed zinc phosphate particles to be effective and lead to nucleation. It was found that the zinc phosphate fine particles adsorbed easily grow due to the high concentration of soluble zinc component (zinc ion concentration). In other words, it was found that the chemical conversion property is greatly improved by using a surface conditioner in which not only water-insoluble phosphate fine particles but also a soluble zinc component (typically water-soluble zinc ion) coexists. .

  On the other hand, in general, the surface conditioning treatment liquid has a pH of 8 or more in order to prevent the surface of the material from rusting during the surface conditioning process or before entering the subsequent phosphate treatment process. In most cases, sodium phosphate or the like is used to maintain this pH. However, zinc ions, which are considered to occupy most of the soluble zinc component in a treatment solution having a pH of 8 or higher, precipitate as zinc hydroxide or become zinc phosphate by sodium phosphate used for pH adjustment. Therefore, it cannot be stably present in the surface conditioning solution as a soluble zinc component (typically zinc ions). For this reason, in this invention, pH is set to 4-8 so that soluble zinc ions do not precipitate. Thereby, it can exist stably also in a surface adjustment processing liquid as a soluble zinc ion, and chemical conversion can be improved. The present invention will be described below.

The present invention (1) is a surface-conditioning treatment solution for forming a metal phosphate film in which zinc phosphate fine particles are dispersed in water, and contains 10 to 2000 ppm of zinc as a soluble component {typically zinc It contains 10 to 2000 ppm of ions (Zn ²⁺ )} and has a pH of 4 to 8.

This invention (2) is a manufacturing method of the metal in which the phosphate coating film was formed including the chemical conversion process which applies a metal to a phosphate chemical conversion liquid, Prior to the said chemical conversion process, zinc phosphate microparticles | fine-particles are in water. Dispersed surface conditioning treatment solution for metal phosphate coating, containing 10 to 2000 ppm of zinc as a soluble component {typically containing 10 to 2000 ppm of zinc ions (Zn ²⁺ ). } And a surface adjustment step of applying a liquid having a pH of 4 to 8 to the metal.

  This invention (3) is the method of the said invention (2) whose metal is a metal structure which has a bag structure.

  The present invention (4) is the method according to the invention (3), wherein the metal component is an automobile body or an automobile part.

The present invention (5) is a method for forming a phosphate coating on a metal surface, including a chemical conversion step in which a metal is applied to a phosphate chemical conversion treatment solution, wherein the zinc phosphate fine particles are dispersed in water prior to the chemical conversion step. A surface conditioning treatment solution for metal phosphate coating conversion treatment, containing 10 to 2000 ppm of zinc as a soluble component {typically containing 10 to 2000 ppm of zinc ions (Zn ²⁺ )} And it is a method characterized by including the surface adjustment process which applies the liquid whose pH is 4-8 to a metal.

  The present invention (6) is the method of the invention (5), wherein the metal is a metal structure having a bag structure.

  This invention (7) is the method of the said invention (6) whose metal structure is a motor vehicle body or a motor vehicle part. The present invention is described in detail below.

≪Surface conditioning solution≫
The surface conditioning treatment liquid according to the present invention is a liquid medium containing water as a main component and containing zinc phosphate fine particles and a soluble zinc component as essential components. Hereinafter, each component will be described in detail.

(Zinc phosphate fine particles)
The zinc phosphate fine particles according to the present invention are not particularly limited as long as they are insoluble in a liquid medium, but are preferably zinc phosphate fine particles having an average particle diameter of 1 μm or less. Here, the “zinc phosphate” may be a salt containing at least phosphoric acid (PO ₄ ) and zinc, and may contain other metals or may be in the form of a hydrate. Preferred is Zn ₃ (PO ₄ ) ₂ .4H ₂ O (for example, hopite) in which the anion is only phosphoric acid and the cation is only zinc. The “average particle diameter” refers to a value measured with a submicron particle analyzer (Coulter N4 type: manufactured by Coulter). The lower limit value of the average particle diameter is not particularly limited, but is, for example, 0.001 μm.

(Soluble zinc component)
The soluble zinc component according to the present invention is not particularly limited as long as it is a zinc component that is soluble in a liquid medium, and examples thereof include zinc ions and complexes containing zinc ions, and are typically zinc ions. .

Here, the concentrations of “zinc as a soluble component” and “zinc phosphate fine particles as an insoluble component” in the claims and the present specification are determined by the following method. First, when based on the raw material used, it can be calculated by calculation from the amount of the added water-soluble zinc salt and water-insoluble zinc phosphate fine particles. Moreover, when analyzing the processing liquid for surface adjustment directly, it can guide | induce according to the following method. Normally, no significant difference occurs between the two methods.
Method: In the surface conditioning treatment liquid according to the present invention, zinc phosphate fine particles are uniformly dispersed and adjusted so as not to precipitate in a normal state. For this reason, the zinc phosphate microparticles | fine-particles in a surface adjustment process liquid are settled and separated by centrifugation. Therefore, it is necessary to select a centrifugal separation condition in which all zinc phosphate fine particles settle. As an example, using a Himac CP80WX separation ultracentrifuge manufactured by Hitachi Koki Co., Ltd., centrifugation is performed at 50000 rpm for 1 hour. Thereby, a supernatant part turns into a completely transparent liquid. Thereafter, the obtained supernatant is subjected to analysis as a soluble component. In this state, the component present in the precipitation layer is referred to as “insoluble”, and the component present in the supernatant layer is referred to as “soluble”. In addition, regarding the measuring method of a soluble zinc component (as zinc), for example, the supernatant liquid from which zinc phosphate fine particles have been removed by the above-described centrifugal separation method is analyzed by chelate titration, ICP emission analysis, or the like. Regarding the measurement method of the zinc phosphate fine particles, for example, a certain amount of the surface conditioning treatment liquid is collected, and after removing moisture by drying under reduced pressure, the weight is measured again. The weight of all the components contained is calculated | required and this is made into Ag / L. Next, a certain amount of the supernatant obtained by the previous centrifugation method is also collected and dried to obtain the weight, and the component contained in the supernatant is defined as Bg / L. Since (A-B) g / l is an insoluble component contained in the surface conditioning liquid, this is defined as the weight of the zinc phosphate fine particles. In practice, a part of the dispersant or the like may be precipitated as an insoluble component, but the amount is very small and may be practically used.

  The surface conditioning treatment liquid according to the present invention is, for example, a dispersant for stabilizing zinc phosphate fine particles in a liquid medium (for example, a dispersant described in paragraph Nos. 0023 to 0036 of JP-A-2004-68149). Alternatively, it may contain a rust preventive agent that prevents rust that may be caused by the pH being in the acidic range.

(Liquid medium)
The liquid medium of the surface conditioning treatment liquid according to the present invention (which functions as a dispersion medium for zinc phosphate fine particles and a solvent for a soluble zinc component) is an aqueous medium containing 80% by weight or more of water. Here, various organic solvents can be used as the medium other than water, but the content of the organic solvent should be kept low, preferably 10% by weight or less, more preferably 5% by weight or less of the aqueous medium. It is. Considering environmental problems in particular, it is more preferable to use only water.

(Amount of each component)
The content of the essential zinc phosphate fine particles is preferably 10 to 2000 ppm (mg / l), more preferably 20 to 500 ppm. Moreover, the soluble zinc component (typically zinc ion), which is an essential component, is ineffective when the concentration of the soluble zinc component (typically zinc ion) to be added is too small, and economically disadvantageous when the amount is too large. Therefore, it is preferably 10 to 2000 ppm (as zinc), more preferably 20 to 1000 ppm (mg / l). Moreover, the dispersing agent which is an arbitrary component is 1-2000 ppm, for example, and a rust preventive agent is 1-2000 ppm.

(Physical properties of surface conditioning solution)
The pH of the surface conditioning solution according to the present invention is about 4-8, preferably about 6-7. This is because zinc hydroxide (typically zinc ions) precipitates in a soluble form in the solution because it is precipitated as zinc hydroxide when the pH is raised. Furthermore, if the pH is set too acidic, rust may be generated during the surface adjustment step or after the phosphate coating conversion treatment is performed thereafter, so that the above range is also meaningful in this respect. . Here, a comparison with the prior art is shown. Patent Document 8 states in claim 1 that “a method of treating a metal surface comprising a surface conditioning treatment step and a phosphate chemical conversion treatment step, wherein the surface conditioning treatment step has a zinc ion concentration of 300 on a weight basis. ˜1000 ppm, which is carried out by a surface conditioner containing phosphate ions, and the phosphating treatment process is described as “...”. It is shown to be a colloid of zinc acid fine particles. In addition, it is clear that when the liquid containing phosphate ions and zinc ions is adjusted to pH 7.0 to 7.5, water-insoluble zinc phosphate crystals are obtained. In addition, in the examples, a surfactant is added to a concentrated solution having a zinc phosphate concentration of 40% and dispersed using a ball mill, so that only water-insoluble zinc phosphate fine particles are used. It is clear and different from the present invention. Patent Document 9 discloses a surface conditioner using zinc phosphate particles and zinc nitrite. However, as described above, nitrite is mixed in order to prevent the material surface from rusting during the surface conditioning process or before entering the subsequent phosphating process, Zinc nitrite is proposed as one of the salts. The reason why the zinc salt is used is that the zinc contained in the chemical conversion solution is selected in paragraph [0025] in order to prevent the surface conditioning agent from being brought into the chemical conversion process and accumulating foreign metals. It is written. In the examples, zinc nitrite was added to the dispersion of zinc phosphate, and the pH was adjusted to 9 to 10 with caustic soda. At this pH, the zinc ions became zinc hydroxide and were insoluble in water. Is clear and substantially free of water-soluble zinc ions. That is, unlike the present invention, the zinc phosphate dispersion does not contain water-soluble zinc ions. As described above, the above reference is expressed as a surface conditioner containing zinc ions, but is substantially different from the present invention because it does not contain a water-soluble zinc component. It is clear that it does not give any suggestions.

≪Method for manufacturing surface conditioning solution≫
The method for producing a surface conditioning treatment liquid according to the present invention includes a step of dispersing zinc phosphate fine particles in the above-described aqueous medium and a step of dissolving a water-soluble zinc compound in the above-described aqueous medium. An insoluble zinc phosphate crystal (hopeite) is used as a raw material, and this is dispersed in water together with a dispersant and the like, and then finely divided using a pulverizer such as a ball mill. Thereafter, if necessary, an additive such as a rust inhibitor is added, and an aqueous solution of a water-soluble zinc compound is added to adjust the pH. For pH adjustment, an acid such as nitric acid, a typical acid such as sodium hydroxide, or an alkali is used. However, this procedure is only an example, and is not limited at all. Here, various water-soluble zinc salts can be used, and specific examples include zinc sulfate, zinc nitrate, zinc acetate, zinc formate, zinc chloride, zinc fluoride, and zinc silicofluoride. However, even if other zinc salts are water-soluble, any salt can be expected to be effective because it is present as a soluble zinc component (typically zinc ions) in an aqueous solution. In addition, since water-insoluble salts such as zinc oxide and zinc hydroxide do not readily dissolve in the phosphating solution, they cannot be immediately used as a crystal raw material for the phosphate coating, and the effect cannot be obtained.

≪Usage method of surface conditioning solution (manufacturing method of metal with phosphate coating) ≫
(Mechanism of action)
This technology first adsorbs zinc phosphate particles that are insoluble on the surface of the workpiece by using a surface conditioner that contains insoluble zinc phosphate particles and a soluble zinc component (typically zinc ions). In the phosphate chemical conversion treatment step, the zinc concentration of the chemical conversion treatment liquid is substantially increased by the soluble zinc component (typically zinc ions) adhering to the surface of the object to be treated. Thus, the chemical conversion is further improved. By doing so, the adsorbed zinc phosphate fine particles are prevented from dissolving or falling off in the chemical conversion solution and failing to function sufficiently, and countless crystals are precipitated on the surface of the object to be processed by acting efficiently as crystal nuclei. Therefore, it is a technology that makes it possible to greatly improve the chemical conversion.

  In particular, according to the conventional chemical conversion treatment method, the processing solution components are consumed and diluted in the inner plate portion during the chemical conversion treatment. Ion) is not in time, resulting in poor formation. On the other hand, according to the chemical conversion treatment method using the surface conditioning treatment liquid according to the present invention, since the surface conditioning treatment liquid contains a soluble zinc component (typically zinc ions), the chemical conversion treatment is particularly important. As a result of being able to promote the formation of many crystal nuclei in the initial stage, the chemical conversion is greatly improved. Thus, the soluble zinc component concentration (typically the zinc ion concentration) in the chemical conversion solution can be increased in a state where a large number of water-insoluble zinc phosphate microcrystals that are the source of crystal nuclei are adsorbed on the inner plate. is important.

  Hereinafter, the surface conditioning treatment liquid according to the present invention is particularly effective, and the surface conditioning treatment liquid is used as an example when the surface treatment is performed on the inner and outer surfaces of the metal structure having a bag structure (a phosphate coating is formed). The method for producing the metal will be specifically described.

(Applicable)
The object of the surface treatment is a metal structure (automobile body or automobile part) having a bag structure, and at least a part thereof is a cold-rolled steel plate and / or an aluminum alloy plate. For example, the metal structure to be processed is composed of two or more metal plates like a car door and has a bag-like structure. Here, as a definition regarding the bag structure portion, an area ratio of the area of the opening to the surface area inside the bag structure portion is used as a scale in the present invention. As a specific example, in the case of a cube composed of six square plates each having a size of 10 cm, the internal area is calculated to be 600 cm ² , but one hole is provided in each plate located above and below the cube. Assuming opening, if the area of one hole is 30 cm ² , the area of the opening is 60 cm ² in total, and the ratio of the area of the opening / the area inside the bag structure is 10%. When the area of one hole is 0.3 cm ² , the ratio of the area of the opening / the area of the bag structure is calculated as 0.1%. Hereinafter, the area ratio between the area of the opening of the bag structure portion and the area inside the bag structure portion in the metal structure having the bag structure portion is defined as “opening / area ratio of the bag structure portion”. . In the surface treatment using the surface conditioning treatment liquid according to the present invention, the area ratio of the opening / bag structure portion is preferably 0.1 to 10%, more preferably 0.2 to 7%, 0.5 ~ 5% is most preferred. The area ratio of the opening / bag structure is an area ratio at which a remarkable effect is recognized in the surface treatment using the surface conditioning treatment liquid according to the present invention.

(Method)
The method of forming the phosphate coating on the metal surface according to this example (a method for producing a metal having a phosphate coating) includes a chemical conversion step in which the metal is applied to a phosphate chemical treatment liquid, and the chemical conversion step. Prior to this, a surface adjustment step of applying the surface adjustment treatment liquid according to the present invention to a metal is essential. Here, in general, the treatment is performed in the following steps, but the treatment method is performed by immersion treatment in each step. Typically, this is a chemical conversion treatment process for an automobile body that is widely used.
(1) Degreasing (2) Washing with water (multistage)
(3) Surface adjustment (4) Phosphate coating conversion treatment (5) Water washing (multistage)
(6) Pure water washing

  The present invention greatly improves the chemical conversion inside the bag structure (inner plate part), which was difficult to produce a sufficient film by the conventional phosphate film conversion treatment method, and is dense and fine like the outer plate part. It was possible to form a phosphate coating. Thereby, the corrosion resistance of the inner plate part can be improved. Further, according to the present invention, costly measures such as facility modification are not necessary, and it is not necessary to change the phosphate coating conversion treatment liquid, so that the cost associated with these changes does not occur. Further, since there is no great influence on the physical properties of the film, there is a great merit that it can be easily applied to the current line.

(Metal construction)
FIG. 1 shows a simulated metal structure (a metal structure imitating an automobile part) used for demonstrating the effects of the present invention. A cold rolled steel plate SPCC (JIS 3141) or aluminum plate (JIS 5052) having a plate thickness of 0.8 mm and 70 × 150 mm was used to form a box having a bag structure as shown in FIG. SPCC or aluminum plates were placed on the top and bottom two sheets so that the distance between them was 10 mm, and the side surfaces were plastic plates and holes with a diameter of 10 mm were formed in two places. The upper and lower two SPCC or aluminum plates are fixed by the side plastic plates, and the processing solution enters and exits only through the holes on the two sides. This simulated metal component was treated by immersing it in a treatment solution, and disassembled after the treatment to observe the state of chemical conversion treatment. In addition, the area ratio of the opening part / bag structure part of this metal structure is 0.7%.

(Alkaline degreasing solution)
In both Examples and Comparative Examples, fine cleaner E2001 (registered trademark: manufactured by Nippon Parkerizing Co., Ltd.) was used, and it was confirmed that the sample was degreased by immersion treatment and completely wetted.

(Surface conditioner)
Table 1 shows the composition of the treatment liquid for surface adjustment used in Examples and Comparative Examples. The zinc phosphate fine particles were obtained by pulverizing Zn ₃ (PO ₄ ) ₂ .4H ₂ O reagent with a ball mill using zirconia beads. The zinc phosphate fine particles were made into a suspension, filtered through a 5 μm paper filter, and the average particle size of the filtrate was measured with a submicron particle analyzer (Coulter N4 type: Coulter). As a result, it was 0.31 μm. In addition, regarding the content of zinc phosphate fine particles and the soluble zinc concentration in Table 1, the added zinc phosphate fine particles are insoluble in the liquid medium (in this example, water). Based on the fact that it completely dissolves in the liquid medium (water in this example), the amount added was estimated as the amount present in the liquid. Moreover, the presence form of the soluble zinc component in a liquid is estimated to be a zinc ion substantially. However, some samples were analyzed for precipitates and supernatants by the centrifugation described in the specification, but it was confirmed that they were almost as estimated. After addition of the soluble zinc salt, the pH was adjusted with nitric acid and an aqueous sodium hydroxide solution so that the pH became a predetermined pH.

(Phosphate treatment solution)
In both Examples and Comparative Examples, Palbond SX35 (registered trademark: manufactured by Nippon Parkerizing Co., Ltd.) was used after adjusting to a concentration generally used for zinc phosphate treatment for automobiles. The processing steps are shown below.

(Processing process)
(1) Alkaline degreasing 40 ° C., 120 seconds immersion (2) Washing at room temperature, 30 seconds Immersion (3) Surface conditioning Room temperature 30 seconds See immersion, Examples and Comparative Examples (4) Phosphate treatment 35 ° C., 120 seconds immersion ( 5) Water washing Room temperature, 30 seconds immersion (6) Deionized water washing Room temperature, 30 seconds immersion

(Evaluation method of phosphate coating)
(1) Appearance
By visual observation, the presence or absence of scum and unevenness of the zinc phosphate coating was confirmed. Evaluation was as follows.
◎ Uniform and good appearance
○ Some unevenness
△ Unevenness and scale
× Too much

  Table 1 shows the results of processing in Examples and Comparative Examples. From this, all the examples in which soluble zinc ions were allowed to coexist with insoluble zinc phosphate fine particles showed good chemical conversion. On the other hand, those not containing soluble zinc ions and those having an amount of 10 ppm or less had many unevenness and scales, and good chemical conversion properties could not be obtained. In Comparative Example 6 in which soluble zinc ions were added, the pH was adjusted to 9, so that zinc ions were precipitated as zinc hydroxide and were not substantially present as soluble zinc ions, so that good chemical conversion was not obtained. It was.

FIG. 1 is a diagram showing a simulated metal structure used in an example of the present invention.

Claims (7)

  In a surface conditioning treatment solution for metal phosphate coating conversion treatment in which zinc phosphate fine particles are dispersed in water, it contains 10 to 2000 ppm of zinc as a soluble component and has a pH of 4 to 8. Surface treatment solution. In the manufacturing method of the metal in which the phosphate film was formed including the chemical conversion process which applies a metal to a phosphate chemical conversion liquid,
Prior to the chemical conversion step, zinc phosphate fine particles are dispersed in water, a surface conditioning treatment solution for metal phosphate coating chemical conversion, containing 10 to 2000 ppm of zinc as a soluble component, and having a pH of A method comprising a surface conditioning step of applying a liquid of 4 to 8 to a metal.   The method according to claim 2, wherein the metal is a metal structure having a bag structure.   The method according to claim 3, wherein the metal component is an automobile body or an automobile part. In a method of forming a phosphate coating on a metal surface, including a chemical conversion step of applying a metal to a phosphate chemical conversion treatment solution,
Prior to the chemical conversion step, zinc phosphate fine particles are dispersed in water, a surface conditioning treatment solution for metal phosphate coating chemical conversion, containing 10 to 2000 ppm of zinc as a soluble component, and having a pH of A method comprising a surface conditioning step of applying a liquid of 4 to 8 to a metal.   The method according to claim 5, wherein the metal is a metal structure having a bag structure.   The method according to claim 6, wherein the metal component is an automobile body or an automobile part.

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