JPS6137997A - Surface treatment of aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To improve the wear and corrosion resistances by electrodepositing a prescribed metal in the micropores in an anodic oxide film and carrying out chemical conversion treatment. CONSTITUTION:Al or an Al alloy is anodically oxidized to form an anodic oxide film, and one or more kinds of metals selected among Cu, Ag, Zn, Fe, Sn and Ni are electrodeposited in the micropores in the anodic oxide film. Chemical conversion treatment is then carried out to seal the micropores. By this method the wear and corrosion resistances are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of aluminum or aluminum alloy. More specifically, after an anodic oxide film is formed on aluminum or an aluminum alloy, metal is electrochemically deposited into the fine pores of the anodic oxide film, followed by chemical conversion treatment and pore sealing. The present invention relates to a method for surface treatment of aluminum or aluminum alloy with corrosion resistance.

Conventionally, a method is known in which aluminum or an aluminum alloy is anodized, colored by secondary electrolysis, and then sealed. This coating generally has good weather resistance, heat resistance, corrosion resistance, and can be colored in various colors, so it is widely used as decorative building materials with increased added value.

however.

Anodic oxide films are used near coasts exposed to salt damage, in automobile parts for cold regions, and in marine structures.

For other special purposes related to medical care, etc.

At present, it cannot be said that it has sufficient corrosion resistance. By the way, so-called chemical conversion coatings, such as chromate coating on zinc and phosphate coating on iron, are widely used as a base treatment method for painting because they improve the adhesion of the coating and further improve corrosion resistance. It has been. In recent years, electrolytic chromate treatment has also been used to further improve corrosion resistance after decorative plating such as noble metal plating or chrome plating. However, chemical conversion coatings are fragile, have poor scratch resistance, and are weak against physical external forces, so there are limits to their use.

The present invention improves the above problem by anodizing aluminum or aluminum alloy.

After electrolyzing in an aqueous solution containing metal salts to deposit metal into the fine pores of the anodic oxide film, a chemical conversion treatment is performed by immersion or electrolysis to form a chemical conversion film.2. The present invention was completed based on the discovery that, through treatment, an anodic oxide film containing a chemical conversion film has better corrosion resistance than a normal anodic oxide film.

Next, the present invention will be specifically explained. A conventional electrolyte can be used as the anodizing bath. For example, in addition to sulfuric acid baths, sulfuric acid/oxalic acid mixed baths, oxalic acid baths, various inorganic acid baths, organic acid baths, mixed baths of these baths, and baths in which alcohol or the like is mixed or added, etc. can all be used. . In addition, the electrolysis conditions are the conventional DC method, AC method, and AC/DC superposition method.

Current reversal method 1 A method utilizing the recovery effect is used, and the bath temperature, current density, and voltage may be those commonly used.

Next, a so-called secondary electrolytic coloring technique is used to deposit metal into the fine pores of the anodic oxide film. At this time, the bath composition, bath temperature, and power waveform.

Electrolytic conditions such as current density for 1 hour need to be set appropriately depending on the metal. Further, as the metal to be electrodeposited, a metal containing one or more of copper, silver, zinc, iron, tin, and nickel is used. Preferably zinc.

Iron shows better results.

Next, chemical conversion treatment is performed. At this time, as the chemical conversion treatment, one or more of chromate treatment, sulfurization treatment, phosphate treatment, titanium salt treatment, oxalate treatment, oxidation treatment, silicate treatment, etc. can be used. It is preferable to use one or more of treatment, phosphate treatment, sulfurization treatment, oxalate treatment, etc., and chromate treatment and phosphate treatment are even more preferable. Also, as the chemical conversion treatment bath, use one that does not damage the anodic oxide film. For example, in phosphate treatment, use one with as low a phosphoric acid concentration as possible.

Chemical conversion treatment methods include dipping, spraying, pouring, brushing, and low-cleaning brushing.

Although any method may be used, the chemical conversion treatment method by dipping is easy to operate and provides a uniform film. The chemical conversion treatment conditions need to be appropriately set depending on the metal species electrodeposited into the micropores of the anodic oxide film and the chemical conversion treatment bath. To explain this phenomenon, when metal is electrodeposited into the fine pores of the anodic oxide film and then immersed in a chemical conversion treatment bath, electrochemical reactions occur between the metal deposited in the fine pores of the anodic oxide film and the chemical conversion treatment bath. A reaction occurs.

Insoluble compounds are deposited on the surface of the deposited metal, creating a thin, corrosion-resistant film. Finally, sealing is performed.

The sealing treatment may be performed by a commonly used treatment method.

Next, an example will be described.

Example I JIsA1080p-HI3 (50 x 50 x 0°8 cm) was used as a test piece, and was degreased with alkaline and washed with water.

Next, it was immersed in a 10% nitric acid bath (at room temperature) to remove smut, washed with water, and then anodized under the following conditions.

A 10 μm anodized film was obtained.

Composition Sulfuric acid 150g/C as metal aluminum content 1
g/j! Electrolysis conditions: DC IA/di, 20° C., 30 minutes Next, iron was electrodeposited into the micropores of the anodic oxide film under the following conditions.

Composition Ferrous sulfate 100g/C citric acid 5g/I) Boric acid 30g/I1. Glycerin 15cc/It Electrolytic conditions AC 13V, 25℃, 10 minutes Next, the test piece was immersed in a zinc phosphate aqueous solution, and chemical conversion treatment was performed under the following conditions to react with the metal in the micropores to form phosphoric acid. A zinc coating was applied.

Composition: Chemister 29P (Chemister Co., Ltd.) 60g
/A Processing conditions: 50 to 60°C, followed by water washing for 5 minutes, and 1. A commonly used pore sealing process was performed under the following conditions.

Composition Alumite sealer (Nihon Kagaku Sangyo Co., Ltd.) L
og/* Processing conditions: 90-100°C for 30 minutes, finally washed with water and dried to obtain a corrosion-resistant anodic oxide film.

Example 2 JISA5052P-H24 (50x50x0°8)
was used as a test piece, pretreated in the same manner as in Example 1, and copper was electrodeposited into the micropores of the anodic oxide film under the following conditions.

Composition: Sulfuric acid 15g/C copper sulfate Log/Il Electrolytic conditions: AC 13V, 25°C, 5 minutes Next, the test piece was immersed in a chromic acid-based aqueous solution, and chemical conversion treatment was performed under the following conditions to remove the copper in the micropores. A chromate film was obtained by reacting with

Composition Sunchromate) W-6 (Kobayashi Kasei Co., Ltd. % Formula %) Then washed with water, sealed in the same manner as in Example 1, and finally washed with water and dried to obtain a corrosion-resistant anodized film containing a copper chromate film. It was done.

Example 3 JISA3003P-HI3 (50'x50xO.

8B) was used as a test piece, and pretreated in the same manner as in Example 1.

Zinc was electrodeposited into the micropores of the anodic oxide film under the following conditions using the test piece as a cathode.

Composition Zinc sulfate 350 g/(!, Ammonium sulfate 30 g/It, Boric acid 30 g/It Electrolytic conditions DC 0.5
A/d i, 30℃.

Next, the test piece was immersed in a chromic acid-based aqueous solution for 10 minutes, and a chemical conversion treatment was performed under the following conditions to react with the metal in the micropores to form a chromate film.

Composition Sun Chromate W-6 (Kobayashi Kasei Co., Ltd. Formula %) Next, it was washed with water, and sealed in the same manner as in Example 1. Finally, it was washed with water and dried to obtain a corrosion-resistant anodized film with a built-in zinc chromate film. Ta.

Test pieces treated in Examples 1 to 3, and as comparative examples, test pieces that were anodized and then sealed, and test pieces that were anodized and then subjected to secondary electrolytic coloring of zinc and sealed. The corrosion resistance was compared using an alkali drop test and a CASS test. The results are shown in Tables 1 and 2.

Table 1 Table 2 Table 1 shows test pieces treated in Examples 1 to 3, test pieces treated with anodization treatment and sealing treatment as a comparative example, and secondary electrolytic coloring of zinc after anodization treatment. The corrosion resistance of the sealed test piece was measured using an alkali drop test and the time taken for the film to melt.

Table 2 shows the corrosion resistance using the same test pieces as in Table 1, using a Cath test for 24 hours, and using rating numbers.

A: Coating according to Example 1 B: Coating according to Example 2 C: Coating according to Example 3 D: Anodized coating E, which was subjected to sealing immediately after anodizing treatment After anodizing treatment, secondary zinc electrolytic coloring is performed.

The anodic oxide film that was then sealed has the following effects:
It is very useful industrially.

(11 This is because a chemical conversion film is formed on the inner surface of the anodic oxide film.

A corrosion-resistant coating with good abrasion resistance is obtained and can be used satisfactorily even in highly corrosive environments.

(2) Not only is it corrosion resistant, but the anodic oxide film is colored by secondary electrolysis, so it has excellent weather resistance and heat resistance.

Moreover, a beautiful colored surface can be obtained.

(3) After secondary electrolytic coloring, a chemical conversion treatment is performed by dipping or the like, so the operation is simple and it can be easily incorporated into a normal alumite line.

Claims (1)

[Claims] 1. A surface treatment method in which aluminum or an aluminum alloy is anodized to form an anodized film, and then a metal is electrodeposited into the fine pores of the anodic oxide film to seal the pores. , after electrodepositing metal into the micropores of the anodic oxide film,
A method for surface treatment of aluminum or aluminum alloy, characterized by carrying out chemical conversion treatment and sealing treatment. 2 The metals to be deposited into the micropores of the anodic oxide film of aluminum or aluminum alloy are copper, silver, zinc, iron, tin,
The method for surface treatment of aluminum or aluminum alloy according to claim 1, characterized in that one or more types of nickel are used. 3 Chemical conversion treatments after metal is electrodeposited into the micropores of the anodic oxide film of aluminum or aluminum alloy include chromate treatment, phosphate treatment, sulfidation treatment, oxidation treatment, silicate treatment, titanium salt treatment, and oxalic acid treatment. The method for surface treatment of aluminum or aluminum alloy according to claim 1, characterized in that one or more types of salt treatment or the like are used.