JP2001049450A - Surface treating composition for galvanized steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface treating compsn. capable of imparting excellent corrosion resistance equal to or above that by chromate treatment or phosphate treatment to a galvanized steel sheet and moreover capable of obtaining a surface treated galvanized steel sheet good in adhesion for a coating material. SOLUTION: In water of 1000 pts.wt., (A) a hydrazine derivative of 0.2 to 50 pts.wt. and (B) acid capable of etching zinc of 0.1 to 30 pts.wt. are dispersed or dissolved. Moreover, as to the surface treating method for a galvanized steel sheet, the surface of a galvanized steel-sheet is coated with the surface treating compsn. so as to control the content of a hydrazine derivative to 20-100 mg/m2, and drying is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment composition for galvanized steel sheet having excellent paint adhesion and corrosion resistance, a surface treatment method using the composition, and a surface-treated galvanized steel sheet.

[0002]

2. Description of the Related Art In recent years,
Rust prevention coated steel sheets are required to have excellent corrosion resistance, and instead of conventional cold-rolled steel sheets, surface-treated steel sheets using zinc-based plated steel sheets as substrates are widely used.

Conventionally, chromate treatment and zinc phosphate treatment have been generally performed as surface treatments for galvanized steel sheets, but the toxicity of chromium has been a problem. The chromate treatment has a problem of volatilization of chromate fume in the treatment process, a large cost for wastewater treatment equipment, and a problem of elution of chromate from the chemical conversion coating. Hexavalent chromium compounds are available from IARC (International
l Agency for Researchon Cancer Review) and many other public institutions have designated it as a carcinogen for the human body, and it is extremely harmful.

[0004] In the zinc phosphate treatment, after the zinc phosphate treatment, the rinsing treatment is usually performed with chromic acid, so that there is a problem of the chromium treatment, and a reaction accelerator in the zinc phosphate treatment agent, and waste water such as metal ions. There is a problem of sludge treatment due to elution of metal ions from the treated and treated metal.

As a treatment method other than the chromate treatment and the zinc phosphate treatment, (1) a surface treatment method of treating with an aqueous solution containing aluminum biphosphate and then heating at a temperature of 150 to 550 ° C. -28857), (2)
A method of treating with an aqueous solution containing tannic acid (JP-A-51
And (3) a treatment method using sodium nitrite, sodium borate, imidazole, an aromatic carboxylic acid, a surfactant, or a combination thereof.

However, in the method (1), when a paint is applied thereon, the adhesion of the paint is not sufficient, and in the method (2), the corrosion resistance is inferior. In the method (3),
All have the problem that the corrosion resistance when exposed to a hot and humid atmosphere is poor.

An object of the present invention is to solve the problems of toxicity caused by chromium compounds, wastewater treatment of metal ions and the like, and sludge treatment by elution of metal ions from metals to be treated, such as chromate treatment and zinc phosphate treatment. Provided is a surface treatment composition capable of obtaining a surface-treated galvanized steel sheet which has no problem and can exhibit paint adhesion and corrosion resistance equivalent to or higher than those of chromate treatment and zinc phosphate treatment. That is.

[0008]

Means for Solving the Problems The present inventors have found that the above object can be achieved by an aqueous surface treatment composition containing a specific corrosion resistance improver and an acid serving as an etching agent, and completed the present invention. I came to.

That is, in the present invention, (A) 0.2 to 50 parts by weight of a hydrazine derivative and (B) 0.1 to 30 parts by weight of an acid capable of etching zinc are dispersed or dissolved in 1000 parts by weight of water. It is intended to provide a surface-treating composition for a zinc-based plated steel sheet, characterized by the above.

[0010] Further, the present invention provides the above-mentioned surface treatment composition on a surface of a galvanized steel sheet, wherein the hydrazine derivative is 20 to 20%.
An object of the present invention is to provide a method for surface-treating a galvanized steel sheet, which is applied and dried so as to have a concentration of 100 mg / m2.

Further, the present invention provides a galvanized steel sheet which has been surface-treated with the above-mentioned surface treatment composition.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the surface treatment composition of the present invention will be described.

The composition of the present invention is a surface treatment composition in which a hydrazine derivative (A) and an acid (B) capable of etching zinc are dispersed or dissolved in water.

[0014] Specific examples of the hydrazine derivative (A) hydrazine derivative (A) is, for example, carbohydrazide, hydrazide propionate, salicylic hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecane geo hydrazide, isophthalic acid dihydrazide, thiocarbohydrazide And hydrazide compounds such as 4,4'-oxybisbenzenesulfonylhydrazide, benzophenone hydrazone and aminopolyacrylamide; and pyrazole, 3,5-dimethylpyrazole, 3-methyl-5-pyrazolone, 3-amino-5-methylpyrazole and the like. Pyrazole compounds; 1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-1,
2,4-triazole, 5-amino-3-mercapto-
1,2,4-triazole, 2,3-dihydro-3-oxo-1,2,4-triazole, 1H-benzotriazole, 1-hydroxybenzotriazole (monohydrate), 6-methyl-8-hydroxy Triazole compounds such as triazolopyridazine, 6-phenyl-8-hydroxytriazolopyridazine, 5-hydroxy-7-methyl-1,3,8-triazaindolizine; 5-phenyl-1,2,3,4- Tetrazole, 5-mercapto-1
Tetrazole compounds such as -phenyl-1,2,3,4-tetrazole; 5-amino-2-mercapto-1,3,3;
4-thiadiazole, 2,5-dimercapto-1,3,
Thiadiazole compounds such as 4-thiadiazole; maleic hydrazide, 3,6-dichloropyridazine, 6-methyl-3-pyridazone, 4,5-dichloro-3-pyridazone, 4,5-dibromo-3-pyridazone, 6-methyl And pyridazine compounds such as -4,5-dihydro-3-pyridazone. Above all, 5-member ring or 6
Pyrazole compounds and triazole compounds having a membered ring structure and having a nitrogen atom in the ring structure are preferred. These hydrazine derivatives can be used alone or in combination of two or more.

Acid (B) capable of etching zinc The acid (B) capable of etching zinc may be any acid that is stable in the composition of the present invention and capable of etching zinc. For example, hydrofluoric acid , Hydrobromic acid, hydroiodic acid, borofluoric acid, mineral acids such as fluorotitanic acid, hydrosilicofluoric acid, sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid; acetic acid, chloroacetic acid, trichloroacetic acid, lactic acid and Organic acids such as tartaric acid can be mentioned. These can be used alone or in combination of two or more. Among these, phosphoric acid can be suitably used.

The acid (B) capable of etching zinc dissolves zinc on the plating surface when the composition of the present invention is applied to a galvanized steel sheet, and the zinc ion generated by the dissolution is a hydrazine derivative (A). It is considered that a strong film having excellent corrosion resistance can be formed on the plating surface in combination with the above.

In the surface treatment composition of the present invention, the amount of each component is 0.2 to 50 parts by weight, preferably 1 to 1 part by weight of hydrazine derivative (A) per 1000 parts by weight of water.
The amount of the acid capable of etching (B) zinc is 0.1 to 30 parts by weight, preferably 1 to 5 parts by weight.

The composition of the present invention contains the above-mentioned hydrazine derivative (A) and an acid (B) capable of etching zinc as essential components in water, and further comprises an organic solvent if necessary.
A neutralizing agent, an oxidizing agent and the like can be appropriately contained.

As the organic solvent, any solvent can be used without particular limitation as long as it can dissolve or disperse the hydrazine derivative (A) and the acid (B) capable of etching zinc.

The neutralizing agent is added as necessary to neutralize the film-forming organic resin to make it aqueous, and when the film-forming organic resin is a cationic resin, Can use an acid such as acetic acid, lactic acid or formic acid as a neutralizing agent.

The oxidizing agent has a function of assisting the action of the acid (B) capable of etching zinc, and includes, for example, hydrogen peroxide, perborate, permanganate, nitrite, nitrate, chlorate. , Bromate and the like. Among them, hydrogen peroxide can be suitably used.

Next, a method for treating the surface of a galvanized steel sheet of the present invention using the surface treatment composition of the present invention will be described.

The surface treatment method of the present invention is characterized in that the surface treatment composition of the present invention is applied to the surface of a galvanized steel sheet and dried.

Examples of the galvanized steel sheet to be surface-treated include a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, an iron-zinc alloy-coated steel sheet, a nickel-zinc alloy-coated steel sheet, and an aluminum-zinc alloy-coated steel sheet (for example, “galvalume”). , Alloy-plated steel sheets sold under the trade name "Galfun"). Further, as the zinc-based plated steel sheet, a zinc-based plated steel sheet which has been subjected to a chemical conversion treatment such as a chromate treatment, a zinc phosphate treatment, and a composite oxide film treatment can be used.

The coating amount of the surface treatment composition of the present invention on the zinc-based plated steel sheet is not particularly limited, but usually, the amount of the hydrazine derivative is 20 to 100 mg / m 2,
It is preferably in the range of 30 to 80 mg / m 2 from the viewpoint of corrosion resistance, workability, and the like.

When the surface treatment composition of the present invention is applied to a galvanized steel sheet, the viscosity of the composition of the present invention is usually in the range of, for example, about 5 to 100 mPa · s depending on the amount of application with water. The surface treatment can be performed by applying by a coating method such as roll coater coating, spray coating, brush coating, squeezing coating in which the excess liquid is removed by squeezing after liquid coating, and heating and drying. Drying conditions are not particularly limited as long as the applied surface treatment composition can be dried, but when the object to be coated is continuously dried in a sheet form, the ambient temperature is usually 100 to 250. It is preferable to heat at 10C for about 10 to 100 seconds (the maximum temperature of the steel sheet is about 80C to 150C).

The surface-treated galvanized steel sheet obtained by the surface treatment method of the present invention has excellent corrosion resistance and workability, and can be used as it is as a rust-proof steel sheet, but also has excellent coating film adhesion. Thus, an upper layer coating can be further formed on the surface-treated galvanized steel sheet. The composition for forming the upper layer coating may be appropriately selected depending on the purpose, and various coating compositions can be used. Examples of the coating composition include a lubricating coating forming composition, a highly corrosion resistant coating forming composition, a primer coating, and a colored top coating. The composition for forming a lubricating film, the composition for forming a highly corrosion-resistant film or a primer paint may be applied and dried, and then a colored top coat may be applied thereon.

[0028]

The present invention will be described more specifically with reference to the following examples and comparative examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.

Example 1 Water was added to a 36% hydrofluoric acid aqueous solution to obtain a 3% hydrofluoric acid aqueous solution. Separately, 10 g of 3,5-dimethylpyrazole and 90 g of water were blended in a mayonnaise bottle,
Put glass beads and disperse with paint shaker,
A dispersion having a solid content of 10% was obtained. 100 parts of this dispersion and 3
333.3 parts of a 30% hydrofluoric acid solution and 586.7 parts of water were mixed to obtain a surface treatment composition.

Examples 2 to 17 and Comparative Examples 1 to 3 Aqueous solutions of each acid having a concentration of 3% were obtained by using those shown in Table 1 below as the types of acids capable of etching zinc. The dispersion shown in Table 1 was used to obtain a dispersion having a solid content of 10% by dispersing in water, and these were mixed with water so that the amount of each component with respect to 1000 parts of water was as shown in Table 1 below. Each surface treatment composition was obtained in the same manner as in Example 1.

[0031]

[Table 1]

In Table 1, the amount of each component is indicated by the amount of an effective component for an acid capable of etching zinc, and the amount of a solid content for a hydrazine derivative.

Preparation of Test Coated Plates Using the surface treatment compositions obtained in Examples 1 to 17 and Comparative Examples 1 to 3, the following coating method (1) and coating method (2)
, Each test coated plate was prepared.

Coating Method (1) (Examples 18 to 34 and Comparative Examples 4 to 6) An electrogalvanized steel sheet having a thickness of 0.6 mm and a coating weight of 20 g / m ^{2 on} one side was degreased and washed, and then the Example 1
To 17 and Comparative Examples 1 and 2 were applied by a spinner so that the coating amount of the hydrazine derivative was 50 mg / m ^2, and baked for 15 seconds to PMT (the highest temperature of the steel sheet). Was baked for 15 seconds under the condition that the temperature became 100 ° C. to obtain each treated plate. In Comparative Example 5, processing was performed under the same conditions as in Example 18, and in Comparative Example 6, Example 28 was performed.
The treatment was performed under the same conditions as described above. Next, Cosmer 2050 (manufactured by Kansai Paint Co., Ltd., trade name, acryl / silica composite resin solution) was applied on each of the resulting processing plates to a dry film thickness of 3 μm.
m and baked for 20 seconds under the condition that the PMT is 120 ° C. to prepare each test coated plate.

Comparative Example 7 An electrogalvanized steel sheet having a thickness of 0.6 mm and a coating adhesion amount of 20 g / m ^{2 on} one side was degreased and washed, and then a surface treatment composition was not applied. Painted to a thickness of 3 μm, PMT 120 ° C
It was baked for 20 seconds under the following conditions to obtain a test coated plate.

Each test coated plate was subjected to a corrosion resistance test. The test results are shown in Table 2 below. The test was performed according to the following test method.

Corrosion resistance: A salt water spray test specified in JIS Z2371 was performed on the test coated plate sealed at the end surface and the back surface of the test coated plate for up to 240 hours. The degree was evaluated according to the following criteria. a: no white rust is observed; b: white rust is less than 5% of the coating area; c: white rust is 5% or more and less than 10% of the coating area; d: white The degree of rust generation is 10% or more and less than 50% of the area of the coating film. E: The degree of white rust generation is 50% or more of the area of the coating film.

[0038]

[Table 2]

Coating Method (2) (Examples 35 to 51 and Comparative Examples 8 to 10) A hot-dip galvanized steel sheet having a thickness of 0.4 mm and a coating weight of 120 g / m ^{2 on} one side was degreased and washed, and then the Each of the surface treatment compositions obtained in Examples 1 to 17 and Comparative Examples 1 to 3 was applied with a spinner so that the coating amount of the hydrazine derivative was 50 mg / m ^2, and under the condition that the PMT was 100 ° C. Baking was performed for 15 seconds to obtain a treated plate. In Comparative Example 9, processing was performed under the same conditions as in Example 35, and in Comparative Example 10, processing was performed under the same conditions as in Example 45. Then, a KP color 8000 primer (a modified epoxy resin-based primer paint manufactured by Kansai Paint Co., Ltd.) was applied on the treated plate so that the dry film thickness was 5 μm, and the PMT was 210 μm.
C. for 20 seconds to form a primer coating, and then apply KP color 15 on the primer coating.
80 white (manufactured by Kansai Paint Co., Ltd., thermosetting polyester resin paint, white) is applied to a dry film thickness of 20 μm, and baked at a PMT of 215 ° C. for 40 seconds to form an upper layer coating film. A test coated plate was prepared.

COMPARATIVE EXAMPLE 11 A hot-dip galvanized steel sheet having a thickness of 0.4 mm and a coating weight of 120 g / m ^{2 on} one side was degreased and washed, and was not coated with a surface treatment composition. 2) A primer coating film and a top coating film were formed in the same manner as in (1) to obtain a test coated plate.

With respect to these test coated plates, the adhesion, corrosion resistance and moisture resistance of the upper layer coating film were tested according to the following test methods. The test results are shown in Table 3 below.

Test Method Adhesion of Upper Layer Coating Film: With respect to the test coating plate, eleven vertical and horizontal scratches reaching the substrate with a knife were cut in a grid pattern to make 100 squares of 1 mm square. A cellophane pressure-sensitive adhesive tape was adhered to the grid, and the tape was instantaneously peeled off. The degree of peeling of the upper layer coating film was evaluated according to the following criteria. a: no peeling of the upper coating film is observed at all; b: 1-2 peeling of the upper coating film is observed; c: 3 to 10 peeling of the upper coating film are observed; d: peeling of the upper coating film 11 or more are observed.

Corrosion resistance: After sealing the end surface and the back surface of the test coating plate having the upper coating film cut into a size of 70 × 150 mm, a 4T bent portion (0 with the coating surface outside) was placed on the top of the test coating plate. (A part bent at 180 degrees with four spacers each having a thickness of .4 mm)) and a cross-cut portion is provided below the test coated plate according to JISZ2.
The salt spray test specified in 371 was performed for 1000 hours.
In the coated plate after the test, the degree of occurrence of white rust at the 4T bent portion, the blister width of the cross cut portion, and the blister occurrence degree of the general portion (the central portion without processing and cutting) were evaluated according to the following criteria.

[Degree of generation of white rust at 4T bent portion] a: no generation of white rust is observed, b: slight generation of white rust, c: considerable generation of white rust, d: significant generation of white rust [Blister width of cross cut portion] a: One side blister width from cross cut is less than 1 mm, b: One side blister width from cross cut is 1 mm or more, 2
less than 5 mm, c: 5 when the one-sided blister width from the cross cut is 2 mm or more
mm: d: One-sided blister width from the cross cut is 5 mm or more, [degree of blistering in the general part] a: no blistering is observed, b: slight blistering is recognized, c: considerable blistering D: remarkable blistering is observed.

Moisture resistance: The test coated plate having the upper and lower coating films sealed with the end surface and the back surface was subjected to JIS K54.
A moisture resistance test was performed according to 9.2.2. The temperature inside the humidity tester box is 49 ° C and the relative humidity is 95-100.
%, The test time was 1000 hours. The degree of blistering of the coating film of the test coated plate after the test was evaluated according to the following criteria. a: no blistering is observed; b: slight blistering is observed; c: considerable blistering is observed; d: significant blistering is observed.

[0046]

[Table 3]

[0047]

EFFECT OF THE INVENTION The composition of the present invention is applied to a galvanized steel sheet.
Surface treatment with excellent corrosion resistance and coating film adhesion can be performed, and it can be used instead of the conventional surface treatment such as zinc phosphate treatment and chromate treatment. The composition of the present invention does not generate sludge at the time of surface treatment, and does not use a chromium compound, so that there is no problem of toxicity due to the chromium compound. Therefore, problems in working environment and environmental conservation can be eliminated.

The zinc-coated steel sheet surface-treated with the composition of the present invention, when a coating film is formed thereon, can have excellent adhesion to the coating film. It can also be used for applications such as building materials, home appliances, and automobile parts.

Claims (5)

[Claims] 1. A method wherein (A) 0.2 to 50 parts by weight of a hydrazine derivative and (B) 0.1 to 30 parts by weight of an acid capable of etching zinc are dispersed or dissolved in 1000 parts by weight of water. Surface treatment composition for zinc-based plated steel sheets. 2. The composition according to claim 1, wherein the acid (B) capable of etching zinc is at least one acid selected from phosphoric acid and hydrofluoric acid. 3. The composition according to claim 1, wherein the hydrazine derivative (A) is a pyrazole compound or a triazole compound. 4. The surface treatment composition according to claim 1, wherein the hydrazine derivative is present in an amount of 20 to 10 on the surface of a zinc-based plated steel sheet.
A method for surface-treating a galvanized steel sheet, which is applied and dried so as to be 0 mg / m2. 5. A galvanized steel sheet which is surface-treated with the surface treatment composition according to claim 1.