JPS6148598B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tertiary electrolytic coloring method for aluminum or its alloys, and more specifically to a method for coloring aluminum or its alloys, which can prevent changes in color tone due to changes in the concentration of an intermediate treatment solution. This invention relates to a tertiary electrolytic coloring method.

The tertiary electrolytic coloring method for aluminum or its alloys (hereinafter referred to as aluminum materials) consists of the steps of pretreatment, anodization, intermediate treatment, and electrolytic coloring, and is a method for obtaining special color tones that cannot be obtained with the conventional Asada method. It is. Among the above steps, intermediate treatment involves sulfuric acid,
It is carried out by passing an alternating current through an acidic treatment solution such as phosphoric acid, and its purpose is to remove the barrier layer that exists between the aluminum material base and the porous layer of the anodic oxide film formed by anodic oxidation. The purpose is to form a second porous layer therein.

In the conventional intermediate processing, a desired color tone was obtained by setting the elapsed time from the start of energization, but it had the drawback that when the concentration of the processing liquid changed, the obtained color tone also changed accordingly. For example, to obtain a green tone, use a processing solution containing 150g/sulfuric acid.
It is necessary to apply electricity at AC5V for 25 minutes, but if the sulfuric acid concentration drops to 100g/, the color becomes gray even under the same electricity application conditions. Of course, it is theoretically possible to obtain a constant color tone by keeping the concentration of the treatment liquid constant; however, in practice, it is nearly impossible to maintain the concentration of the treatment liquid constant.

As a result of intensive research in search of a solution to the above-mentioned problems, the present inventor found that by making the energization time the same after reaching the intermediate treatment peak current, even if the concentration of the intermediate treatment solution changes, the current is substantially the same. The present inventors have discovered that it is possible to obtain a color tone of 1, and have completed the present invention.

That is, in the intermediate treatment step of the tertiary electrolytic coloring method of aluminum materials, the present invention makes the current application time the same after reaching the peak current,
It is characterized by preventing changes in color tone due to fluctuations in the concentration of the intermediate processing solution.

The point in time when the intermediate processing peak current is reached can be easily detected using a current/voltage recorder, etc., and the subsequent energization time can also be easily set by interlocking a timer, etc., so the present invention improves not only work efficiency but also By preventing variations in color tone, etc., it is also possible to improve product yield.

Note that the method of the present invention can be effectively applied not only to intermediate treatment liquids containing sulfuric acid but also to cases where other intermediate treatment liquids such as phosphoric acid are used.

For example, when the following anodized aluminum material is subjected to intermediate treatment under the following conditions, the relationship between the treatment time and the current value is approximately as shown in FIG. 1.

Aluminum material A1200P 2×70×150 (mm) Intermediate treatment conditions H ₂ SO ₄ 150g/Voltage AC 6V Bath temperature 20±1℃ Treatment time 20 minutes In order to obtain the desired color tone, the corresponding treatment time is A It has been set based on the time between -B. However, if the concentration of the processing solution is different, the graph showing the relationship between processing time and current value in Figure 1 will be different, so even if intermediate processing is performed according to the set processing time, the color tone obtained by coloring processing will be different. turns out to be different from what I expected. For example, to obtain a green tone, it is necessary to perform intermediate treatment for 25 minutes at 150 g of H ₂ SO ₄ at 5 VAC, but the concentration of H ₂ SO ₄
At 100g/, it turns gray under the same conditions. The present invention prevents such changes in color tone due to fluctuations in processing liquid concentration, and therefore makes the current application time the same after reaching the peak current. Examples of the present invention will be described below.

Example 1 Using the same aluminum material as above,
Figure 2 shows the results of examining the relationship between treatment time and current for H ₂ SO ₄ concentrations of 100 g/ and 150 g/. In the figure, A indicates the time when the peak current of each concentration is reached.

Two aluminum materials that had been anodized using a conventional method were subjected to intermediate treatment for 1 minute from the point at which the peak current was reached under each H ₂ SO ₄ concentration condition (ie, from A to B). When the obtained intermediately treated aluminum materials were colored in a coloring bath having the following composition at AC10V for 1 minute, both aluminum materials were colored green.

Coloring bath composition SnSO ₄ 5 g/ H ₂ SO ₄ 10 g NiSO ₄ 25 g CH ₃ C ₆ H ₃ (OH) SO ₃ H 10 g/ Similarly, at each H ₂ SO ₄ concentration condition, reach the peak current, and continue for another 2 minutes. Intermediate processing was performed (ie, A→C). When the obtained intermediately treated aluminum materials were colored in a coloring bath having the above composition at 14 V for 1 minute, both aluminum materials were colored red.

Example 2 As in Example 1, anodized aluminum material was heated to H ₂ SO ₄ concentrations of 50 g/, 100 g/, 150
Intermediate treatment was performed at AC6.5V and bath temperature of 20±1° C. for 0.5 minutes after reaching the peak current under the conditions of 1.5 g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/g/, intermediate treatment was performed for 0.5 minutes after reaching the peak current at AC6.5V and bath temperature of 20±1°C.
When the obtained intermediately treated aluminum material was colored in a coloring bath having the following composition under the following electrolytic coloring conditions, a gray color close to bronze was obtained in each case.

Coloring bath composition Sn (SO ₃ NH ₂ ) ₂ 7.3 g/ NH ₂ SO ₃ H 25 g/ NiSO ₄ 15 g/ CH ₃ C ₆ H ₃ (OH) SO ₃ H 10 g/ Coloring conditions Voltage AC10 minutes Time 1 minute Bath temperature 20±1℃ Example 3 H ₂ SO ₄ concentration 100g/, 150g/, 200g/
and the energization time after reaching the peak current are each 1.0.
The anodized aluminum material was subjected to intermediate treatment and electrolytic coloring treatment under the same conditions as in Example 2. As a result, a strong green gray color was obtained at all concentrations.

From the above examples, it was confirmed that even if the H ₂ SO ₄ concentration during the intermediate treatment was different, by making the treatment time the same after each peak current was reached, almost the same color tone could be obtained.

The conditions for anodic oxidation of the aluminum material used in the above examples were as follows.

Anodizing conditions Current density 1.5A/m ² hours 35 minutes Film thickness (target) 14μm Bath temperature 20±1℃

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing the relationship between the concentration of each intermediate treatment liquid, the treatment time, and the reached current value, respectively.

Claims (1)

[Claims] 1. In the intermediate treatment step in the tertiary electrolytic coloring method of aluminum or its alloy, by making the current application time the same after reaching the peak current, changes in color tone due to fluctuations in the concentration of the intermediate treatment solution are prevented. An electrolytic coloring method for aluminum or its alloy, characterized by: 2. The method according to claim 1, wherein the intermediate treatment liquid contains sulfuric acid. 3. The method according to claim 1, wherein the intermediate treatment liquid contains phosphoric acid, and the electrolytic coloring method for aluminum or its alloy.