JP3069027B2 - White chromate treatment with excellent chromium elution resistance, corrosion resistance and coating performance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aluminum (hereinafter referred to as "aluminum") or aluminum alloy plated steel sheet, zinc or zinc alloy plated steel sheet, tin or tin alloy plated material, and aluminum or aluminum alloy based material, zinc or zinc alloy based steel. The present invention relates to a chromium hardly soluble white chromate treatment method which is excellent in corrosion resistance and appearance quality after coating performance processing of a non-ferrous metal plated steel plate or a non-ferrous metal material such as a tin or tin alloy material.

[0002]

2. Description of the Related Art Chromate treatment has been used for a long time as a simple rust preventive treatment for metal surfaces, and is roughly classified into electrolytic chromate or reactive chromate containing trivalent chromium as a main component.
There is a coated chromate which contains hexavalent chromium and is dried without washing after coating. In recent years, chromate treatment has been widely used for applications such as home appliances, building materials, and automobiles.
Various performances have been demanded by consumers. For example, uniformity of appearance, appearance quality such as fingerprint resistance, paint adhesion, corrosion resistance when barely used, hardly dissolving chromium to alkali degreasing (chromium elution resistance) and the like are examples. Among these performances, there are those which are hardly compatible with each other, for example, corrosion resistance, particularly, corrosion resistance of a processed portion and hardly dissolving chromium, and it is not technically easy to express all the performances in a well-balanced manner. The insolubilization of chromium is considered to be an important issue to be solved by the responsibility of the material supplier from the viewpoints of consumer protection and global environmental protection, not only from the demands of consumers, especially hexavalent chromium. Measures are urgently required for coating chromate containing a large amount of.

As a known technique for making a chromate hardly soluble, for example, a method of heating a chromate film at a relatively high temperature of 300 ° C., as described in Japanese Patent Application Laid-Open No. Hei 3-215683, is known. However, it is not economical considering the cost of the drying equipment. In addition, Japanese Unexamined Patent Publication No.
As disclosed in JP-A-358082 and JP-A-5-287548, a resin such as polyacrylic acid or a reducing agent such as alcohol is added to a chromate treatment bath, hexavalent chromium is fixed by reduction, and trivalent chromium is a resin. It is also known to crosslink in water. According to this method, the corrosion resistance of the chromate film is improved due to the barrier effect of the resin, but if the film is broken at the processed portion, the self-repairing action by hexavalent chromium does not function, so that the corrosion resistance of the processed portion is not sufficient. Difficulties remain. Also, because a large amount of reducing components are present in the treatment bath,
Poor bath stability. JP-A-61-23767 discloses that a mixture of a water-dispersible organic polymer containing no hydroxyl group and a chromate salt has excellent bath stability. However, the obtained chromate-treated plate has a remarkably large amount of chromium eluted.

JP-A-63-145785 discloses a composition comprising an acrylic polymer emulsion obtained by emulsion polymerization using a polyoxyethylene-polyoxypropylene block polymer emulsifier and a hexavalent chromium compound. It has been disclosed. This composition is 40 ° C due to the effect of the emulsifier.
However, it is stable for 3 weeks or more, but the water resistance and bare corrosion resistance are not sufficient because the emulsifier remains in the dried resin chromate film. In addition, the present inventors have disclosed Japanese Patent Application No. 6-30289.
No. 0 proposes a chromate treatment bath to which reduced chromic acid, phosphonic acid and a water-soluble organic polymer are added. In this case, a chromate film having excellent corrosion resistance, paint adhesion and processing appearance can be obtained, but the organic compound used is 30 g.
/ L or less, the chromium hardly soluble (chromium elution resistance) is not sufficient, and further improvement is needed in this regard.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a white chromate treatment method which is excellent in corrosion resistance and has good paint adhesion while having a low chromium elution. .

[0006]

Means for Solving the Problems The inventors of the present invention increased corrosion resistance by increasing the concentration of an organic polymer compound in a chromate treatment bath containing reduced chromic acid, phosphonic acid and an organic polymer compound as main components. We have found that a white chromate treatment solution with excellent chromium elution resistance can be obtained without deteriorating paint adhesion and appearance after treatment, and succeeded in development. That is, the gist of the present invention is that (a) reduced chromic acid having a composition ratio of Cr ³⁺ / Cr ⁶⁺ of 3/7 to 7/3 is converted to chromic anhydride on the surface of a non-ferrous metal plated steel sheet or a non-ferrous metal material. (B) a phosphoric acid compound having a weight ratio of 0.5 to 3.0 with respect to chromic anhydride conversion of the reduced chromic acid, and (c) an anhydride of the reduced chromic acid. Silica and / or silicate colloidal silica in a weight ratio of 0.5 to 5.0 relative to chromic acid, and (d) a phosphonic acid or phosphonate compound in an amount of 1.0 to 20 g / l, and (E)
Water-soluble or water-dispersible organic polymer compound 30 g / l
A chromate treatment liquid containing super and is applied, dried by heating, and converted to Cr amount of 7.5 to 100 mg / m ² per one surface.
This is a white chromate treatment method which is excellent in chromium elution resistance, corrosion resistance and coating performance of a non-ferrous metal plated steel sheet or a non-ferrous metal material characterized by forming a chromate film of

The features and effects of each component constituting the hardly soluble chromate treatment liquid having excellent corrosion resistance, coating performance, and appearance after treatment, which are objects of the present invention, will be described in detail below. (I)
As the reduced chromic acid, a chromic acid aqueous solution whose composition ratio of Cr ³⁺ / Cr ⁶⁺ is adjusted to 3/7 to 7/3 by reacting an aqueous solution of chromic anhydride with a reducing agent is used. The concentration of reduced chromic acid in the chromate treatment solution was 7.5 with chromic anhydride.
The concentration is restricted to a range of 100 g / l, and the concentration to be used is determined by the application method and conditions. The reduced chromic acid in which Cr ⁶⁺ is partially reduced to Cr ³⁺ is prepared by the following method. That is, an inorganic anion (for example, phosphate ion or the like) is added to a high-concentration chromic anhydride aqueous solution, and an organic reducing agent is added.
Adding inorganic reducing agent, Cr ³⁺ by reduction reaction Cr ⁶⁺
Change to As the reducing agent, an organic compound such as starch, saccharides and alcohol, or an inorganic compound such as hydrazine and hypophosphorous acid is used.

[0008] When the composition ratio of Cr ³⁺ / Cr ⁶⁺ is less than 3/7, a large amount of soluble Cr ⁶⁺ is contained in the formed chromate film, so that the film is colored and the post-painting corrosion environment is reduced. When exposed, paint adhesion, so-called secondary paint adhesion, and post-paint corrosion resistance deteriorate. On the other hand, Cr ³⁺ / C
If the composition ratio of r ⁶⁺ exceeds 7/3, the chromate treatment bath tends to gel over time, and the corrosion resistance deteriorates. Therefore, the composition ratio of Cr ³⁺ / Cr ⁶⁺ in the reduced chromic acid (a) is restricted to the range of 3/7 to 7/3, preferably 5/5 to 6/4.

If the concentration of the reduced chromic acid in the chromate treatment liquid is less than 7.5 g / l, it is difficult to form a chromate film satisfying the corrosion resistance and coating performance, and if the concentration exceeds 100 g / l. The tendency of the chromate treatment bath to gel with time increases. Therefore, the concentration of the reduced chromic acid of (a) is 7.5 to 100 g / l, preferably 10 to 60 g / l in terms of chromic anhydride.
1 range.

Further, the chromate treatment liquid of the present invention is used for improving the uniform coating property, corrosion resistance, and coating performance of the phosphoric acid compound (b) and the chromate treatment liquid for the purpose of improving the whiteness of the chromate film. (C) Silica and / or silicate colloidal silica is added. (B) Phosphoric acid compounds include phosphoric acid (H ₃ PO ₄ ) and polyphosphoric acid (H
₂ P ₂ O ₇ , H ₅ P ₃ O ₁₀ , H ₆ P ₄ O ₁₃ ), and ammonium salts, Al salts, and Mg salts thereof. These may be used alone or in combination of two or more.

(B) The amount of the phosphoric acid compound to be added is 0.5 to 0.5 with respect to 1 of reduced chromic acid in (a) in terms of chromic anhydride.
It is regulated in the range of 3.0. If the amount of the (b) phosphoric acid compound is less than 0.5 with respect to (a) reduced chromic acid, a white chromate film is not easily formed, and the amount of addition is 3.0 with respect to the reduced chromic acid. If it exceeds, the chromate film is easily dissolved in water, and the corrosion resistance deteriorates. Therefore, (b) the amount of the phosphoric acid compound added is
(A) It is in the range of 0.5 to 3.0, preferably 0.75 to 2.0 with respect to the reduced chromic acid.

The silica (iii) and / or the silicate colloidal silica (ii) are added in the range of 0.5 to 5.0 with respect to (a) 1 of reduced chromic acid in terms of chromic anhydride. (C) When the amount of colloidal silica added is less than 0.5 with respect to (a) reduced chromic acid, uniform coating properties are deteriorated, and thus the appearance performance and corrosion resistance, which are the object of the present invention,
It is difficult to secure the coating performance. On the other hand, (c) the amount of colloidal silica added is (5) based on (a) reduced chromic acid.
If it exceeds 0, there arise problems such as deterioration of the working adhesion of the chromate film and appearance of interference color and deterioration. Therefore, (c) the amount of colloidal silica added is 0.5 to 5.0, preferably 1.5 to 3.5, relative to (a) reduced chromic acid.

As the colloidal silica (c) used in the present invention, a fine particle colloid having an average particle size of 1 to 100 μm is mainly used, and the primary or secondary average particle size is 500 to 3, depending on the desired appearance. Colloidal silica having a relatively large particle size of 000 mμ may be added in combination. Further, in the present invention, in order to form a white type chromate film excellent in the desired corrosion resistance and coating performance, the following phosphonic acid or a salt compound thereof is 1.0%.
２０20 g / l are added. Phosphonic acid is represented by the following formula (I):
(IV).

[0014]

Embedded image

[0015]

Embedded image

[0016]

Embedded image

[0017]

Embedded image

[0018]

Embedded image

Also, one or more compounds selected from these water-soluble salts may be used. The phosphonic acid or its salt compound selected from the above is added alone or in combination of two or more to a chromate bath. Among the phosphonic acids, especially hydroxyalkyl diphosphonic acids and aminoalkyl phosphonic acids and their salt compounds are easily dissolved in a chromic acid solution, and solution preparation and handling on an industrial scale are relatively easy, and are practically preferable. .

When the amount of the (d) phosphonic acid added is 1.0
If the amount is less than g / l, the function and effect of the phosphonic acid, which is the object of the present invention, that is, the surface cleaning by the etching action on the surface of the material to be treated, the uniform formation of the chromate film and the anticorrosion effect due to the inclusion in the film are not sufficient. Since it is sufficient, the intended excellent corrosion resistance and coating performance cannot be obtained. Also (d)
If the amount of the phosphonic acid exceeds 20 g / l, the effect of adding the phosphonic acid is saturated, and the stability of the treatment bath is deteriorated by promoting the reduction of Cr ^{6+ in} the chromate treatment bath. Therefore, (d) the amount of the phosphonic acid added to the chromate treatment bath is 1.0 to 20 g /
l, preferably in the range of 1.5 to 10 g / l.

Further, in the present invention, a water-soluble or water-dispersible organic polymer compound (e) is added to suppress chromium elution from the chromate film. Organic polymer addition not only improves chromium elution resistance,
It has the effect of improving coating performance and corrosion resistance. As the organic polymer compound, anionic polyacrylic acid having a carboxyl group and its co-polymer, maleic acid co-polymer, and vinyl acetate co-polymer are used. These organic polymer compounds are mainly added and used alone, but two or more kinds may be added in combination.

The amount of the organic polymer compound added is 30 g.
/ L needs to be controlled. This is presumed to be because when the amount exceeds 30 g / l, the sealing effect of the organic polymer compound appears remarkably, and as a result, the elution amount of chromium decreases. When the addition amount is less than 30 g / l, as shown in FIG. 1, the hardly soluble chromate film intended in the present invention is hardly obtained. However, there is a concern that the long-term stability of the processing solution may be impaired as the amount of the organic polymer compound increases, but the amount of the organic compound added may be controlled according to the required chromate film properties. Therefore, the amount of the organic polymer compound to be added is controlled in a range of more than 30 g / l, preferably in a range of more than 30 to 180 g / l.

The relationship between the amount of the organic polymer compound added and the amount of chromium eluted shown in FIG.
Using a g / m ² hot-dip galvanized steel sheet, it was measured by the following treatment liquid composition and chromium elution test. (1) Composition of treatment solution-Chromic acid concentration 20 g / l (Cr3 ⁺ 55%)-Phosphoric acid 20 g / l-Silica colloid 60 g / l-Phosphonic acid 10 g / l-Organic polymer compound 0-220 g / l (2 ) Chromium elution test The amount of chromium on the steel plate before and after immersion in boiling water for 30 minutes is measured by the fluorescent X-ray method

The present invention is configured as described above.
(A) Reduced chromic acid-(b) phosphoric acid compound-(c) roller
Idarsilica- (d) phosphonic acid or salt compound 1
More than species-(e) Water-soluble or water-dispersible organic polymer
Apply chromate treatment liquid consisting of compound to the surface of material to be treated
7.5 to 100 mg / m per side in terms of Cr ^Two 
And dried by heating. How to apply chromate solution
Conventionally, it is possible by a method generally performed. For example,
Apply by dipping or spraying method and draw roll
Method and air knife method to remove excess chromate treatment liquid
Method to adjust the amount of chromate film by wiping, roll coater
Method to adjust the amount of chromate film by
It is. Then, after applying the chromate treatment liquid, heat drying
Treatment is applied.
The known method is adopted. For example, hot air drying, gas
Or electric heating, infrared heating, etc.
In the temperature range of 0-200 ° C, preferably 60-150 ° C
It is dried by heating.

The adhesion amount of the chromate film formed on the surface of the material to be treated by these methods is regulated in the range of 7.5 to 100 mg / m ² per one surface in terms of Cr. When the amount of Cr attached is less than 7.5 mg / m ² , the white appearance uniform appearance which is the object of the present invention is obtained, but the corrosion resistance and the corrosion resistance after coating are insufficient, which is not preferable.
On the other hand, if the Cr adhesion amount exceeds 100 mg / m ² , the adhesion workability of the chromate film deteriorates, and the processing adhesion after coating similarly deteriorates, which is not preferable. Therefore, the amount of the chromate film in the present invention is in the range of 7.5 to 100 mg / m ² , preferably 10 to 60 mg / m ² per one surface in terms of the amount of Cr.

The materials to be treated according to the present invention include Al-plated steel sheets, Al-Si-based alloy-plated steel sheets, Zn-plated steel sheets, Zn-Al-based alloy-plated steel sheets, Zn-Al-Si Alloy plated steel sheet, Zn-
Al-Mg based alloy plated steel sheet, Zn-Fe based alloy plated steel sheet, Zn plated steel sheet by electroplating method, Zn-Ni
Alloy plated steel sheet, Zn-Cr alloy plated steel sheet, Zn
-Various non-ferrous metal plated steel sheets such as Ni-Cr based alloy plated steel sheet, Zn-Fe based alloy plated steel sheet, Sn based alloy plated steel sheet and the like, Al materials, Al-Mg-Si, Al-Mg-Si
-Cu, Al-Mg-Si-Cu-Mn alloy material, Z
Non-ferrous metal materials such as n-material, Zn-Al, Zn-Mg, and Zn-Al-Mg alloy-based materials are exemplified.

In particular, in the application of the method of the present invention, compared to the conventional method, (d) a material to be treated in which the effect of the phosphonic acid or its salt compound is remarkably obtained, that is, a stable oxide film is formed. An extremely effective performance improving effect can be obtained for an aluminum-plated steel sheet, an aluminum alloy-plated steel sheet, a Zn-plated steel sheet, a Zn-alloy-plated steel sheet, and an aluminum material, an aluminum alloy material, a Zn alloy material, etc. by the hot-dip plating method. Further, when the method of the present invention is applied, generally, the material to which no fat or oil is attached is directly used, and the material to which fat or oil is attached is treated with a degreasing solution containing an alkali builder. After the cleaning, a chromate treatment is performed, but not particularly limited thereto. For example, when the surface of the material to be treated is not significantly discolored by the degreasing treatment, the method of the present invention may be applied after the material to which the fat or oil is not adhered after the degreasing and washing treatment with a degreasing agent containing an alkali builder or the like. No problem.

[0028]

EXAMPLES In order to clarify the operation and effect of the present invention, specific examples will be described with reference to several examples and comparative examples. Examples A to G and Comparative Examples a to e Table 1 shows the compositions of chromate treatment solutions constituted by the method of the present invention as examples. Table 2 shows the composition of the chromate treatment liquid used as a comparative example. Next, Table 3 shows the performance evaluation results of the chromate-treated material with respect to the test materials of the chromate-treated solution according to the method of the present invention and the comparative chromate-treated solution using representative examples of various non-ferrous metal materials as test materials. In addition, at the time of chromate treatment, the nonferrous metal material to which fats and oils adhered was degreased with an alkaline degreasing agent containing 10 g / l NaOH and 5 g / l Na ₂ CO ₃ as main components, and then chromate treatment was performed. The material to which no fat or oil was attached was subjected to a chromate treatment as it was, and was subjected to an evaluation test.

The performance of the chromate-treated material was evaluated according to the following method. Evaluation of corrosion resistance The white rust occurrence rate after 240 hours of salt spray test (JIS Z2371) was measured and judged according to the following criteria. ：: No white rust occurred 〇: White rust occurrence rate ≦ 5% △: 5% <white rust occurrence rate ≦ 20% ×: 20% <white rust occurrence rate

Chromium resistance elution rate The amount of chromium adhering before and after immersion in boiling water for 30 minutes was measured by X-ray fluorescence, and the rate of reduction was calculated by the following formula, and judged according to the following criteria. Chromium elution rate (%) = (Cr adhesion amount before immersion−Cr adhesion amount after immersion) / (Cr adhesion amount before immersion) × 100 ：: Elution rate ≦ 5% 〇: 5% <elution rate ≦ 10% Δ: 10 <elution rate ≦ 20% ×: 20 <elution rate

Paint Adhesion After coating and baking a melamine alkyd resin paint of 25 μm, it is immersed in boiling water for 30 minutes. Immediately after the removal, a 2 mm gobang is processed with a 10 × 10 = 100 mass cutter, and the tape is peeled off. The peeling area ratio of the paint peeled off by tape peeling was measured and judged according to the following criteria. ：: no peeling 〇: peeling rate ≦ 5% Δ: 5% <peeling rate ≦ 15% ×: 15% <peeling rate

Appearance after treatment The yellowness (Y1 value) after the chromate treatment was measured with a color computer (model SM-3) manufactured by Kaz Test Instruments Co., Ltd., and evaluated according to the following criteria. ：: Y1 ≦ −1.0 〇: −1.0 <Y1 ≦ 2.0 Δ: 2.0 <Y1 ≦ 5.0 ×: 5.0 <Y1 From these results, the white chromate treatment liquid of the present invention. Non-ferrous metal plated steel sheet or non-ferrous metal material treated by
Excellent appearance after treatment, excellent chromium elution resistance, corrosion resistance and coating performance.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

According to the white chromate treating solution of the present invention,
Non-ferrous metal plated steel sheet such as aluminum or aluminum alloy plated steel sheet, zinc or zinc alloy plated steel sheet, tin or tin alloy plated steel sheet, and aluminum or aluminum alloy based material, zinc or zinc based alloy material, tin or tin based alloy material etc. Chromate treatment with excellent corrosion resistance, paint adhesion, appearance quality after treatment and chromium elution resistance is possible for non-ferrous metal materials.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of chromium eluted from a chromate film when the amount of an organic polymer compound added is changed in the chromate treatment solution of the present invention.

Continuation of the front page (72) Inventor Haruhiko Eguchi 1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Prefecture Nippon Steel Corporation Yawata Works (56) References JP-A-7-180065 (JP, A) JP-A-63-310975 (JP, A) JP-A-6-306630 (JP, A) JP-A-63-270480 (JP, A) JP-A-3-24278 (JP, A) (58) Int.Cl. ⁷ , DB name) C23C 22/00-22/86

Claims (1)

(57) [Claims] 1. The composition of (a) Cr ³⁺ / Cr ^{6+ on} a surface of a non-ferrous metal plated steel sheet or a non-ferrous metal material, having a composition ratio of 3/7 to 7 /
3 is reduced to 7.5 to 100 in terms of chromic anhydride.
g / l, and (b) a phosphoric acid compound having a weight ratio of 0.5 to 3.0 with respect to chromic anhydride conversion of the reduced chromic acid,
(C) silica and / or silicate colloidal silica in a weight ratio of 0.5 to 5.0 with respect to chromic anhydride as reduced chromic acid, and (d) phosphonic acid or phosphonate compound 1 0.020 g / l, and (e) a water-soluble or water-dispersible organic polymer compound containing more than 30 g / l of a chromate treatment liquid, and dried by heating to obtain 7 parts per side in terms of Cr amount. A non-ferrous metal plated steel sheet or a non-ferrous metal material is characterized by forming a chromate film of 0.5 to 100 mg / m ² , which is excellent in chromium elution resistance, corrosion resistance and coating performance.