JP2879451B2 - Electrolytic coloring of aluminum material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a shape member, a plate member, and other products made of aluminum or an aluminum alloy (hereinafter, referred to as an aluminum material in a meaning including all of them). The present invention relates to a method of applying a tinted gray color by an electrolytic treatment.

[Conventional technology]

A method of applying a gray color to an aluminum material by an electrolytic coloring method is described in JP-A-61-204395. In this method, an aluminum material is subjected to an anodizing treatment by a conventional method, and then an electrolytic coloring bath containing a nickel salt and a zinc salt as a main component, a nickel ion masking agent, a supporting electrolyte, and the like, and having a pH of 4.5 or more. The metal is precipitated in the pores of the anodic oxide film so that the weight ratio of nickel: zinc in the precipitate becomes 1: 0.5 to 2.0 by performing the electrolytic treatment in the inside.

However, it is difficult to obtain a true achromatic gray color by this method, and there is a problem that the gray color tends to be yellowish or bluish green.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the conventional gray-based electrolytic coloring method and to provide a method for easily and reliably coloring an aluminum material to an achromatic gray color.

[Means for solving the problem]

The aluminum material coloring method of the present invention, which succeeded in achieving the above object, is an electrolytic solution containing a cobalt salt and a zinc salt or an electrolytic solution containing a nickel salt and a zinc salt after anodizing an aluminum material. by subjecting the gray color based electrolytic coloring process, then admittance values Y ₂₀ by treatment with warm water or hot water is subjected to washing with mild sealing of the device such that 300～30Myuesu, then inert to anodic oxidation coating The anodic electrolysis treatment using an aluminum material as the anode in an electrolytic solution having a pH of 4 to 9 moves the metal deposited at the bottom of the fine pores of the anodic oxide film closer to the surface, and decreases the color anodic oxide film thereby reduced. When the colorimetric value b ^* value obtained by the color difference meter becomes 2 to -2, the DC electrolysis treatment is terminated.

In the electrolytic coloring method of the present invention, the incomplete or unstable gray coloring based on the metal precipitated in the pores of the anodic oxide film in the electrolytic coloring step is surely performed in the final DC electrolytic treatment to obtain an achromatic gray color. Change to color.

Hereinafter, the electrolytic coloring method of the present invention will be described in detail in the order of steps.

The aluminum material is first subjected to an anodic oxidation treatment by a conventional method, and a sufficient thickness (preferably about 5 to 25 μm) is formed on the surface.
An oxide film is formed.

The aluminum material after the treatment is then subjected to a gray electrolytic coloring treatment with an electrolytic solution containing a cobalt salt and a zinc salt or an electrolytic solution containing a nickel salt and a zinc salt. In the electrolytic solution used for this electrolytic coloring treatment, nickel salt includes nickel sulfate, nickel ammonium sulfate, nickel acetate, nickel chloride, etc .; zinc salt includes zinc sulfate, zinc chloride, zinc acetate, etc .; and cobalt salt includes sulfuric acid. Cobalt, cobalt chloride, cobalt acetate and the like can be used, respectively. In addition to these metal salts, boric acid, maleic acid, malonic acid,
One or more electrolytes such as lactic acid, gluconic acid, sulfosalicylic acid, malic acid, tartaric acid, citric acid, and glycolic acid can be added.Furthermore, as a stabilizer, magnesium sulfate, ammonium sulfate, ammonium sulfamate, ammonia Water, magnesium oxide and the like can be added. Electrolysis uses carbon, nickel,
Using zinc, stainless steel, or the like, it is performed by commercial frequency alternating current, polarity conversion pulse wave, or direct current. With this process,
Nickel-zinc eutectoids or cobalt-zinc eutectoids are formed in the fine pores of the anodic oxide film, and the anodic oxide film is usually colored yellowish gray. It has been confirmed that the metal deposition at this point is concentrated at the bottom of the oxide film micropores.

The aluminum material that has been subjected to electrolytic coloring is then
Treat with hot or hot water at ~ 95 ° C for about 1 to 10 minutes, and perform light sealing with washing. At this time, the admittance value Y according to the admittance measurement test (JIS H8683)
Perform so that ₂₀ becomes 300 to 30 μS. If a more thorough sealing is performed, the target color tone change cannot be produced even if the DC electrolytic treatment is performed next. Also, if DC electrolysis treatment is performed with no or insufficient sealing,
A large amount of deposited metal elutes from the opening of the micropores,
It becomes whitish. Water used in the treatment preferably has an electric conductivity of 0.01 to 10 μS / cm, and a small amount of a phosphate, borate, tartrate, acetate, amines, fluoride, etc. May be used. In addition, there is no change in the color tone of the oxide film due to the sealing treatment.

Next, a direct current electrolytic treatment using an aluminum material as an anode is performed in an electrolytic solution having a pH of 4 to 9 and an electric conductivity of about 100 μS / cm to 100 mS / cm. If the pH of the electrolytic solution is not within the above range, metal elution during electrolysis is remarkable, and good results cannot be obtained.

The electrolyte must also be inert to the anodic oxide coating. Specifically, there is an aqueous solution containing one or more of magnesium sulfate, zinc sulfate, ammonium sulfate, boric acid, aqueous ammonia, an amine, particles for anionic electrodeposition paint, or an aqueous solution used for electrolytic coloring of the above. As the counter electrode, carbon, stainless steel, nickel, zinc, or the like can be used. Current density about 1
When electrolysis is performed at 100 A / m ² and a voltage of about 10 to 200 V, the oxide film gradually disappears from yellowish color and becomes an achromatic gray color. When the electrolysis is further continued, the oxide film gradually becomes whitish. Normal,
If the colorimetric values b ^* value is about 2 or less by the color difference meter, because not visually feel almost yellowish, b ^* value is about 2～-
When it becomes 2, the electrolysis is stopped. In this process, it has been confirmed that the metal co-deposited in the micropores of the anodic oxide film moves from the bottom of the micropores to near the surface.

The aluminum material which has been subjected to the electrolytic coloring and the DC electrolytic treatment is subjected to a sealing treatment by a conventional method or a coating treatment with a transparent paint as necessary. When the particles for an anionic electrodeposition paint are used as the electrolyte in the DC electrolysis treatment, the electrodeposition can be performed simultaneously with the DC electrolysis. The color tone does not change further by these finishing processes.

〔The invention's effect〕

According to the method of the present invention as described above, it is possible to easily obtain a colored oxide film having a colorimetric value a ^* value of about 1 to -1 and a b ^* value of about 2 to 2 by a color difference meter. This colored oxide film is of a complete achromatic gray color type that cannot be obtained (at least could not be obtained stably) by a conventional method of only performing an electrolytic coloring treatment using a bath containing a metal salt. . The corrosion resistance and abrasion resistance are superior to those of the conventional electrolytic colored anodic oxide film. No discoloration was observed in the 500-hour sunshine weather meter test (ΔE = 0.4), and the weather resistance was extremely excellent.
Therefore, the achromatic gray aluminum material obtained by the method of the present invention can be used for a wide range of applications as an interior / exterior material for buildings or other structural materials.

〔Example〕

Hereinafter, the present invention will be described with reference to examples. In each example, a colorimeter CR-200 manufactured by Minolta Camera Co., Ltd. was used for color measurement. As reference data, the results of actual measurement of achromatic samples in the standard color sample book for paint (Japan Paint Manufacturers Association, 1988 edition, P version) with the above color difference meter are shown below.

Example 1 An aluminum material (A1050P) on which an anodized film having a thickness of about 12 μm was formed by a conventional method using a sulfuric acid bath was prepared by using nickel sulfate 30 g /, zinc sulfate 10 g /, gluconic acid 30 g /, ammonium sulfate 10 g /, and magnesium sulfate. 20g /, pH5.9
When the electrolytic treatment was carried out for 5 minutes at a commercial frequency of 16 V in an aqueous solution of the above, the oxide film turned yellowish gray. This was immersed in industrial water (60 μs / cm) heated to 85 ° C. for 10 minutes to wash and seal the anodized film. After this treatment, the degree of sealing is Y ₂₀ = 200 μS, the colorimetric value is L ^* value 49, a ^*
Value 0.1, b ^* value 3.5.

Then, pH in the aqueous solution with magnesium 100 g / sulfuric acid adjusted to 7.5 with aqueous ammonia and the aluminum material for 2 minutes DC electrolysis at a current density of 2A / m ² as an anode, achromatic gray color (L ^* value 51, a ^* value 0.3, b ^* value 1.9) were obtained.

Thereafter, in order to further improve the corrosion resistance, a complete sealing treatment was performed in water at 95 ° C. to which a sealing aid (alumite sealer) was added.

Example 2 An aluminum material (A6063S) on which an anodized film having a thickness of about 9 μm was formed by a conventional method using a sulfuric acid bath was used as an aqueous solution of nickel sulfate 25 g / zinc acetate 25 g / malonic acid 20 g / magnesium sulfate 40 g / When an aluminum material was used as a cathode and subjected to electrolytic treatment at 25 V DC for 3 minutes, the oxide film turned yellowish light gray. Thereafter, it was immersed in an aqueous solution of ammonium borate 1 g / 75 ° C. for 10 minutes to wash and seal the anodic oxide film. The degree of sealing after the treatment was Y ₂₀ = 250 μS, and the colorimetric values were L ^* value 58, a ^* value 0.2,
b ^* Value was 3.2.

Next, 20 g of zinc sulfate adjusted to pH 7.5 with aqueous ammonia
/, In an aqueous solution of ammonium sulfate 10g /, direct current electrolysis at 60V for 3 minutes using aluminum material as anode,
After air drying, electrostatic coating with a transparent paint gave a beautiful light gray color (L ^* value 60, a ^* value 0.4, b ^* value 1.5).

Example 3 An aluminum material (A1100P) on which an anodized film having a thickness of about 20 μm was formed by a conventional method using a sulfuric acid bath was prepared using 64 g of cobalt sulfate, 2 g of zinc sulfate, and 60 g of magnesium sulfate.
, In an aqueous solution of boric acid 20 g /
When the electrolytic coloring treatment was performed at 30 A / m ² for 5 minutes, the oxide film turned yellowish gray. This was immersed in a 200 ppm aqueous solution of triethanolamine at 90 ° C. for 3 minutes to wash and seal the anodic oxide film. The degree of sealing after this treatment is
Y ₂₀ = 150 μS, colorimetric values are L ^* value 51, a ^* value 0.1, b ^* value
4.3.

Next, in an aqueous solution containing 10% of anionic transparent electrodeposition paint particles (Nippon Paint Co., Ltd., PM # 6000), direct current electrolysis is performed at 150 V for 3 minutes using an aluminum material as an anode to coat the surface of the anodic oxide film. After the film is formed, it is baked and dried to obtain an achromatic gray color (L ^* value 51, a ^* value 0.7, b ^*
2.0).

Claims (1)

(57) [Claims] An aluminum material is subjected to anodizing treatment, followed by a gray-colored electrolytic coloring treatment with an electrolytic solution containing a cobalt salt and a zinc salt or an electrolytic solution containing a nickel salt and a zinc salt, followed by warm water or admittance values Y ₂₀ is treated with hot water performs washing and mild sealing of the device such that 300～30Myuesu, then the anode of the aluminum material in an electrolytic solution of inert pH4~9 against anodized film The metal deposited at the bottom of the fine pores of the anodic oxide film is moved to the vicinity of the surface by performing a direct current electrolytic treatment, and the colorimetric value b ^{* of} the colored anodic oxide film, which is reduced by the color difference meter, is 2 to A method for electrolytically coloring an aluminum material, wherein the DC electrolytic treatment is terminated when the value becomes -2.