JPS5873796A - Electrolytic pigmentation method for aluminum or its alloy - Google Patents

Abstract

PURPOSE:To carry out a secondary electrolytic pigmentation state with a small electric current in a shorter time by immersing Al or an Al alloy having a formed anodic oxide film in an aqueous soln. contg. a zinc compound and a mineral acid for a fixed time. CONSTITUTION:Al or an Al alloy having a formed anodic oxide film is immersed in an aqueous soln. contg. a zinc compound and a mineral acid for a fixed time. It is then subjected to secondary AC electrolytic pigmentation in an electrolytic bath contg. a metallic salt. Thus, a desired color tone can be provided in the electrolytic pigmentation stage with a small electric current in a shorter time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic coloring method for aluminum or its alloys, and more specifically, the present invention relates to an electrolytic coloring method for aluminum or its alloys, and more specifically, the present invention relates to an electrolytic coloring method for aluminum or its alloys, which enables a desired color tone to be obtained in a shorter time with a small current in the electrolytic coloring process. This article relates to a method for electrolytically coloring the alloy.

Conventionally, the method of immersing an anodized film of aluminum or its alloy in an electrolytic bath containing a metal salt and applying alternating current to color the film is a well-known technique known as the Asada method, and is widely practiced in industry. The metal salts most commonly used in the Asada method are salts of nickel, tin, etc., and when colored, they all give a bronze color tone. The colored oxide film obtained in this way has excellent weather resistance, so
Coupled with its color, it is widely used in building materials such as curtain walls and satsushi.

However, in order to obtain a deep color tone using metal salts such as nickel or tin, it usually requires a long coloring time of 15 minutes or more and a current of 2 to 10 A per unit, which requires improvement in productivity and There have been requests for the development of improved methods from the perspective of saving electricity usage.

With the purpose of solving or improving the above-mentioned drawbacks of the prior art, the present inventor has conducted intensive research and found that, prior to the implementation of secondary electrolytic coloring of aluminum or its alloy, aluminum, minilum, etc. Alternatively, by introducing an intermediate step of immersing the alloy, the inventors discovered that the secondary electrolytic coloring step could be carried out in a shorter time and with a smaller electric current, leading to the completion of the present invention.

That is, the present invention provides a method for secondary electrolytically coloring an anodic oxide film of aluminum or its alloy by alternating current in an electrolytic bath containing a metal salt, in which the anodic oxide film on which the anodic oxide film has already been formed is applied prior to performing the secondary electrolytic coloring. Aluminum or its alloys in an aqueous solution containing zinc compounds and mineral acids'
It is characterized by being immersed in water for a certain period of time.

Generally, the electrolytic coloring process for aluminum or its alloys includes degreasing, water washing, etching, water washing, smut removal, water washing,
The bath composition for the electrolytic coloring was a tin compound of 5 to 10%.
1n! , mineral acid 20-30 P/13, -=-y'I
k Compound 10-20 F! -/Z, organic acid 5-15y-
/g.

It consists of The coloring conditions depending on the bath composition and the resulting color tone are shown in the table below.

As is clear from this table, in the conventional coloring method, in order to obtain a deep color, electrolytic coloring had to take a long time of 15 minutes or more.

In the electrolytic coloring method according to the present invention, in the series of steps as described above, intermediate treatment and water washing steps are inserted after anodization and subsequent water washing, and then electrolytic coloring is performed. The intermediate treatment step is immersion for a certain period of time in an aqueous solution containing a zinc compound and a mineral acid, as shown above: , are preferable, and phosphoric acid, hydrochloric acid, nitric acid, sulfuric acid, chromic acid, etc. can also be used as mineral acids, but in particular phosphoric acid, the concentration of these zinc compounds and mineral acids in the aqueous solution can be appropriately selected within a wide range. Although it is possible, from a practical standpoint, it is appropriate that the raw salt compound is ~150P#. Also, the temperature of the treated aqueous solution is 2
The range of 0 to 60°C is preferable, but the immersion time varies depending on the type and concentration of the zinc compound and mineral acid used, the temperature of the treatment solution, etc., but from a practical point of view
A radius of ~25 minutes is suitable.Examples of the present invention will be shown below.

Example m The target color tone was a bronze color with a color measurement value (L value) of 26 by a color difference meter, and a sample with no intermediate treatment under the following coloring conditions and a sample with intermediate treatment under the following intermediate treatment conditions were subjected to secondary Electrolytic coloring was carried out.

Intermediate treatment conditions (a) Bath composition Zinc compound 10? /! Phosphoric acid 10 (3?/A (b) Immersion conditions Liquid temperature 25°C Time 2
0 minute coloring conditions (a) Voltage (AC) (b) Bath composition Stannous acid 81/e Sulfuric acid, 2”5Lt/# Nickel sulfate 15P/# Cresol sulfonic acid 10P# (c) Bath temperature 20±1 ℃ Coloring time and L value after coloring for each sample (Mei 151J
1') is shown in Figure 1. That is, it can be seen that when intermediate processing is performed to obtain the same coloring voltage and brightness required to obtain the target bronze color tone, the coloring can be performed at a lower voltage and in a shorter time.

Example (2) Shading (lightness) of color tone after coloring due to difference in intermediate processing time
Regarding the influence on the intermediate treatment conditions of Example (1), only the immersion time was 0 minutes (no intermediate treatment) 5.10, 15.
20, 25, and 60 minutes, and the coloring voltage was changed to h1, respectively.
A coloring test was conducted by changing to 3.15.18v. The results are shown in FIG.

As is clear from this figure, it is clear that the color becomes darker (that is, the L value decreases) with the intermediate treatment compared to the one without the intermediate treatment (-). Conventionally, it took 7 minutes at 18V AC to obtain the dark bronze color of No. 19, but by applying an intermediate treatment, it took 2 minutes at 18V.
It was obtained in 5 minutes at 10V.

Therefore, an intermediate shell according to the invention! By applying
Compared to the case without conventional intermediate treatment, the electrolytic coloring voltage can be reduced by 6 to 8 cm to obtain the same color density, and at the same time, the coloring time can be shortened by 1.5 to 6 minutes. Therefore, it is possible to significantly reduce the required power.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the coloring time and the obtained lightness (L value) for those subjected to intermediate treatment and those without intermediate treatment, and Figure 2 is a graph showing the relationship between the intermediate treatment time and the brightness (L value) after coloring. L
FIG.

Claims (1)

[Claims] (1)6. In a method of secondary electrolytic coloring of an anodic oxide film of aluminum or its alloy by cross-rolling in a metal salt-containing electrolytic bath, prior to performing the secondary electrolytic coloring, the aluminum or its alloy on which the anodic oxide film has already been formed. A method for electrolytic coloring of aluminum or its alloy, characterized by immersing the aluminum in an aqueous solution containing a zinc compound and a mineral acid for a certain period of time (2). A method for electrolytically coloring aluminum or its alloy in which the mineral acid is phosphoric acid. (3) In the method according to claim 1,
. An electrolytic coloring method for aluminum or its alloy, wherein the galvanizing layer is Zn(OH).