JPS5827360B2 - Electrolytic coloring method for aluminum or its alloys - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic coloring method for aluminum or its alloys which can be colored green, blue or purple in addition to colors ranging from bronze two colors to black.

There are various methods for coloring the anodic oxide film of aluminum or its alloys, but they can be broadly classified into dyeing methods, natural coloring methods, electrolytic coloring methods, and electrolytic coloring methods.

The dyeing method allows dyes to be adsorbed into the micropores of the anodic oxide film, so the color can be freely selected, but it has poor light resistance and the natural coloring method is expensive because it uses a special alloy, while the electrolytic coloring method uses a special organic coloring method. It is expensive because it uses acid and color matching is difficult.

Compared to these coloring methods, the electrolytic coloring method has the problem of using metal salts, but it is now becoming mainstream because the coloring has good light resistance and is inexpensive.

However, the colors that can be colored using this electrolytic coloring method are limited to colors ranging from bronze to black, and it is not possible to color green, blue or purple.

The present invention allows aluminum or its alloy to be colored from bronze to black (bronze, brown, black), as well as green, blue to purple.

Aluminum or its alloys which have been subjected to conventional pretreatment are anodized in a sulfuric acid bath or an oxalic acid bath, and then anodized in a chromium salt bath or a dichromate bath.

The voltage during anodization is an important factor in determining the coloring during AC electrolytic coloring in the next step.

In other words, when the voltage during anodization is low, AC electrolysis produces colors ranging from bronze to black as in the conventional method, and when the voltage during anodization is high, short-time anodization produces green and blue colors using AC electrolysis. Or it can be colored purple.

If the voltage during anodization is too high, the anodic oxide film is likely to be destroyed because high voltage is required during AC electrolytic coloring.

After the anodization, the aluminum or its alloy is washed with water and colored by alternating current electrolysis in an electrolytic bath containing dissolved metal salts.

The metal salt used is an important factor in determining coloration.

The relationship between metal salt and coloring when anodized at high voltage is as follows.

Sn salt and Cd salt...Green Sn salt, Co salt, Fe salt or Zn salt...Blue Sn salt, Ni salt or Cd salt...Purple Sn salt, Cd salt, Co salt, Fe Salt or Zn salt...
Light purple, bronze colored Sn salt, Co salt, Fe salt or Zn salt, Ni salt or C
U salt...Pale blue, light edge color Sn salt, Ni salt or Cd salt, Cd salt...bronze color In the present invention, sulfuric acid or oxalic acid No anodic oxide film is formed and the product will not be colored green, blue or purple unless anodized using a chromium salt bath or dichromate bath.

In the alternating current electrolytic coloring treatment of the present invention, in addition to alternating current, an alternating current weight that periodically changes polarity and has an alternating current component can be used.

Next, examples of the present invention will be shown.

Example 1 An aluminum plate (A1100) subjected to normal pretreatment was 175f! /l sulfuric acid bath, bath temperature 20℃, DC 15V, 2
Anodized for 5 minutes or in a 40 g/l oxialic acid bath at a bath temperature of 29°C and 25 V DC for 20 minutes, then anodized in a 5% aqueous solution of chromium sulfate at room temperature for 3 minutes at 40 V DC,
After washing with water, stannous sulfate 59/l, nickel sulfate 15/l
g/l and sulfuric acid 59/l in an electrolytic bath at 29°C,
The aluminum plate was colored pale purple by AC electrolysis at 15 V AC for about 10 minutes using a carbon rod as a counter electrode.

In this Example 1, an aluminum plate was anodized with a chromium sulfate aqueous solution at 10 V DC for 3 minutes and electrolyzed with AC.
The aluminum plate was colored bronze in 2 to 3 minutes, brown in 5 to 6 minutes, and black in about 10 minutes.

Example 2 In Example 1, a DC 40
V, for 15 minutes, the anodized aluminum plate was colored deep purple.

Example 3 In Example 1, the same amount of cadmium nitrate was used instead of nickel sulfate, and the aluminum plate was colored pale green by AC electrolysis at 30 V AC for 2 to 3 minutes.

Example 5 In Example 1, the same amount of copper sulfate was used instead of nickel sulfate, and the aluminum plate was colored purple.

Example 6 An aluminum plate (AIloo) that had been anodized in a sulfuric acid bath or an oxalic acid bath in the same manner as in Example 1 was anodized in a 5% aqueous solution of chromium potassium sulfate at room temperature at 40 V DC for 4 minutes, and then washed with water. Stannous sulfate 5g/l, nickel sulfate 2011/l, sulfuric acid 10E! The aluminum plate was colored pale purple by alternating current electrolysis for 1 to 2 minutes using a carbon rod as a counter electrode at 30 V alternating current in an electrolytic bath of 25° C./l.

Example 7 An aluminum plate (AIloo) that had been anodized in the same sulfuric acid bath or oxalic acid bath as in Example 1 was anodized with a 6% aqueous solution of potassium dichromate at room temperature for 8 minutes at 25 μDC, and then washed with water. Afterwards, the aluminum plate was colored pale purple by alternating current electrolysis for 10 minutes at 15 V AC with a carbon rod as the counter electrode in an electrolytic bath at 26°C consisting of 5 g/l of stannous sulfate, 1511/l of nickel sulfate, and 10 ji/l of sulfuric acid. .

Example 8 In Example 7, the aluminum plate was anodized in an aqueous solution of potassium dichromate at the same temperature at 4.5 V DC for 8 minutes, and then electrolyzed in an electrolytic bath at the same temperature at 35 V AC for 1 to 2 minutes to give the aluminum plate a pale blue color. Colored.

In each example, 10 g/l of cresolsulfonic acid or LO1 of phenolsulfonic acid was added to the electrolytic bath containing tin salt.
! The addition of /l prevents the precipitation of tin salts and is convenient for alternating current electrolytic treatment.

In Examples 1 and 6.8, the aluminum plate treated with AC electrolytic coloring without anodizing in a chromium salt bath or dichromate bath (such as a chromium salt bath or dichromate bath) became bronze in 2 to 3 minutes, brown in 5 to 6 minutes, It will turn black in about 10 minutes and will not turn green, blue or purple.

Claims (1)

[Claims] 1 Aluminum or its alloys are anodized in a sulfuric acid bath or an oxalic acid bath, then anodized in a chromium salt bath or dichromate bath, and then subjected to alternating current electrolysis in an electrolytic bath containing dissolved tin salts and other metal salts. Electrolytic coloring method for aluminum or its alloys.