JPH0344157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coloring aluminum or an aluminum alloy (hereinafter both will be collectively referred to simply as aluminum).

Conventionally, when coloring aluminum, the generally well-known coloring method is to anodize the aluminum and then conduct AC electrolysis or DC cathode electrolysis in an aqueous solution containing metal salts.Other organic and inorganic coloring methods and physical coloring are also available. Unlike conventional electrolytic coloring methods, the colored film has excellent weather resistance and abrasion resistance, so it is widely applied to color various aluminum materials, including aluminum sash, which is essential for modern architecture. The color tones that can be produced are limited to amper-type or bronze-type ones, and although the shade of coloring can be adjusted to some extent depending on the processing conditions, it is not possible to obtain clear tones of primary colors such as purple, orange, green, and blue. Ta.

The method of the present invention was developed to solve the above-mentioned problem, and is an anodizing process in which two types of waveforms, AC/DC superimposition and DC or AC, are alternately repeated at an arbitrary time ratio when coloring aluminum. An anodic oxide film with a microstructure different from that of a normal anodic oxide film is formed on the surface of the aluminum, and then an electrolytic coloring treatment is performed in an aqueous solution containing metal salts to create an anodized film that is colored by the interference effect of light. This is a method to obtain a colored film with vivid primary color tones.

The method of the present invention will be explained in more detail below.
In the case of this invention, the colored film can be obtained by a simple process of anodizing aluminum and then electrolytically coloring it, but in the first anodizing process, two types of waveforms, AC/DC superimposition and DC or AC, are applied at an arbitrary time ratio. The most significant feature is that anodic oxidation is performed in alternating cycles.

Of the two types of electrolytic treatments in the anodic oxidation process, one has the main purpose of forming an anodic oxide film, the other has the main purpose of modifying the film structure accompanied by current recovery, and the former For the electrolytic treatment that aims to form an anodic oxide film, the electrolytic voltage can be set depending on the bath composition and temperature of the electrolytic bath, and for the latter electrolytic treatment that involves current recovery, , the larger the difference in electrolytic voltage from the former, the stronger the effect of modifying the film structure and the more vivid the color tone, but the longer the current recovery time is required.

In the coloring method of the present invention, an AC/DC superimposed waveform is used for one of the two types of electrolytic treatments, and when AC/DC superimposed electrolysis is used for the purpose of forming an anodic oxide film, compared to the other waveforms, the AC/DC superimposed waveform is This has the effect of easily and uniformly recovering the current in DC or AC electrolysis.On the other hand, when AC/DC superimposed electrolysis is used for the purpose of current recovery, the recovery time is shorter than that in DC electrolysis. Compared to AC electrolysis, it tends to be less likely to cause film breakdown.

In view of the above, the present invention uses AC/DC superimposed electrolysis as one of the two types of electrolytic treatments that are repeated at arbitrary time ratios to quickly and uniformly modify the film structure without damaging the film. This is possible.

At that time, the number of repetitions of the two types of electrolytic treatments was determined. The higher the number of repetitions, the more the film structure is modified.
More than one repetition is required; less than
Only bronze tones or dark primary colors can be obtained as seen with conventional electrolytic coloring.

Regarding the time ratio of the two types of electrolytic treatments,
In the case of electrolytic treatment aimed at forming an anodic oxide film, the current application time to obtain the required film thickness is determined by the electrolytic voltage and the number of repetitions. On the other hand, in electrolytic treatment for the purpose of current recovery, the time when current recovery is completed may be set as the current application time.

As mentioned above, the color tone of the colored film obtained by the method of the present invention is determined by the modification state of the film structure in the anodizing process, so the number of repetitions of the two types of electrolytic treatments, the difference in electrolytic voltage, By determining conditions such as bath composition and bath temperature, it is possible to stably obtain a colored film with vivid primary color tones such as blue, green, orange, and violet through subsequent electrolytic coloring.

Regarding the bath used in the coloring method of the present invention, in the case of an anodizing treatment bath, a commonly used bath containing sulfuric acid, sulfamic acid, oxalic acid, etc. is sufficient, and for electrolytic coloring treatment, a bath containing sulfuric acid, sulfamic acid, oxalic acid, etc. is sufficient. Electrolytic coloring may be carried out in a bath containing metal salts such as tin, copper, cobalt, etc. with a waveform of direct current, alternating current, or the like.

As mentioned above, when the method of the present invention is applied to coloring aluminum, an anodic oxide film having a fine structure can be formed on the surface of aluminum by alternately repeating AC/DC superposition electrolytic treatment and DC or AC electrolytic treatment at an arbitrary time ratio. Then, through a simple process of electrolytic coloring in a water bath containing metal salts, it is possible to obtain a colored film with vivid primary colors due to the interference of light, which improves the weather resistance of the colored film. Coupled with its good hardness and abrasion resistance, it is very useful for coloring various aluminum materials including aluminum sash.

Hereinafter, specific examples of this invention will be listed below.

Example 1 Two plates of aluminum alloy (6063S-T5) were used as samples. A 10V DC anode was applied with carbon as the counter electrode in 150g/l of sulfuric acid and a bath temperature of 33°C. At the same time, a 7V AC voltage was applied between the samples. AC/DC superimposed electrolysis for 25 seconds and 6.5V DC anodic electrolysis for 50 seconds were repeated 30 times to form an anodic oxide film of 6.0 μm each. Next, 5g of stannous sulfate/
1, sulfuric acid 5g/l, carbon as the counter electrode in a room temperature bath, one of the samples was placed as a 10V DC cathode, and the other one was
When each was electrolytically colored for 60 seconds at an AC voltage of 12V, a purple colored film was obtained for both.

Example 2 Two aluminum alloy (6063S-T5) plates were used as samples and anodized in the same manner as in Example 1 to form an anodized film on their surfaces. Next, one of the samples was electrolytically colored in a bath containing 50 g/l of nickel sulfate and 30 g/l of boric acid at room temperature using nickel as the counter electrode with a 15 V AC voltage and the other with a 15 V DC cathode for 60 seconds each. A purple colored film was obtained in both cases.

Example 3 Two plates of aluminum alloy (6063S-T5) were used as samples. Oxalic acid 50g/l, sulfamic acid 50g/l, and a 30V DC anode with carbon as the counter electrode were applied in a bath temperature of 43°C. An anodic oxide film of 9.0 μm is formed by repeating alternating AC/DC superimposed electrolysis for 25 seconds and 25 V DC anodic electrolysis for 50 seconds at a time ratio of 40 times. Next, one of the samples was placed in a room-temperature bath containing 5 g/l of stannous sulfate and 5 g/l of sulfuric acid at 20 V with carbon as the counter electrode.
When electrolytically colored with a DC cathode for 60 seconds, an orange colored film was obtained.

Example 4 Two plates of aluminum alloy (6063S-T5) were used as samples, and a 30V DC anode was applied with oxalic acid at 50g/l and carbon as the counter electrode in a bath temperature of 43℃, and at the same time, a 7V AC voltage was applied between the samples. By repeating alternating AC/DC superimposed electrolysis for 25 seconds and 25V DC anodic electrolysis for 50 seconds 50 times, each
Forms a 12μm anodic oxide film. Next, electrolytic coloring was carried out in the same manner as in Example 3, and a blue film was obtained.

Example 5 Two plates of aluminum alloy (6063S-T5) were used as samples. A 10V DC anode was applied with carbon as the counter electrode in 150g/l of sulfuric acid and a bath temperature of 33°C. At the same time, a 7V AC voltage was applied between the samples. An anodic oxide film of 6.0 μm was formed by repeating alternating AC/DC superimposed electrolysis for 25 seconds and electrolysis for 50 seconds, applying an AC voltage of 7 V between the samples 30 times. Next, when the same direct current electrolytic coloring as in Examples 1 and 2 was carried out, purple colored films were obtained in both cases.

Example 6 Using two aluminum plates (1100P) as samples, applying 17V DC anodic electrolysis with carbon as the counter electrode for 25 seconds in 150g/l of sulfuric acid and a bath temperature of 33℃, and applying 3V DC anode with carbon as the counter electrode. At the same time, AC/DC superposition electrolysis is applied to apply an AC voltage of 7V between the samples.
By repeating the process alternately 25 times at a time ratio of 50 seconds, an anodic oxide film of 9.5 μm each is formed.

Next, electrolytic coloring was carried out in the same manner as in Example 1, and purple colored films were obtained in both cases.

Claims (1)

[Claims] 1. Aluminum or aluminum alloy is anodized by repeating AC/DC superposition electrolytic treatment and DC or AC electrolytic treatment alternately 10 times or more at an arbitrary time ratio, and then electrolytically colored in an aqueous solution containing a metal salt. How to color aluminum or aluminum alloy.