JPS5855593A - Multi-color electrolytic coloration of aluminum of aluminum alloy - Google Patents

Abstract

PURPOSE:To color aluminum or an aluminum allou optional color such as red, blue or green, by a method wherein an anodic oxidation film is formed in an electrolite based on sulfuric acid in a first process and modified in a acidic bath in a second process and the modified coating is electrolyzed in an electrolytic coloring liquid containing a metal salt such as NiSO4 in a third process. CONSTITUTION:An Al material or an Al alloy material is subjected to electrolytic treatment in an electrolyte based on sulfuric acid in a first process to chemically form an anodic oxidation coating having plural fine pores on the ground material. After washing by water, the anodic oxidation material is immersed in an acidic liquid in a second process to increase the diameter of each fine pore as well as to form plural further finer pores to each pore bottom part in a branched form. Subsequently, in a third process, electrolytic coloring treatment is applied in an electrolytic coloring liquid based on a metal salt such as NiSO4 by passing DC, AC or pulse current to develop a gray color, a bronze color, a blue color, a green color or a reddish purple color on the coating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic coloring method for coloring aluminum and its alloys, and the present invention relates to an electrolytic coloring method for coloring aluminum and its alloys. The purpose is to make it possible to color any color such as green, thereby improving the appearance of aluminum and its alloys when used in building materials, etc., as well as expanding the uses of these materials.

According to the present invention, the aluminum or aluminum alloy substrate is pretreated and then electrolytically treated in an electrolyte mainly containing sulfuric acid in the first step, and an anodic oxide film having many micropores is formed on the surface of the substrate. to be chemically formed.

Next &:, After washing the oxide film with water,! In the J2 step, it is immersed in an acid bath, and the anodic oxide film produced in the first step is modified. That is, the acidic bath used in the 9J2 process is one mainly composed of phosphoric acid, or one containing phosphoric acid, nitric acid, sulfuric acid,
Each organic acid may be used alone or in combination with
It is a combination of two things. By immersing it in the above acidic bath, the diameter of the micropore becomes larger than the diameter at the end of the first step, and the bottom of the micropore branches into a large number of even smaller micropores. Furthermore, in the first step, sulfate ions (
804”-) is the anionic species (
For example, phosphate ion, nitrate ion, oxalate ion, etc.]
will be replaced with The film structure or film composition is modified as described above.

After completing the 9J2 process, the substrate and coating are washed with water, and then electrolytically colored in an electrolytic solution containing metal salts in the third step. The entire coating becomes colored when viewed from the outside.

The electrolyte in this third step includes tin, manganese,
Sulfuric acid such as nickel, copper, selenium, silver, etc. ! salt or vinegar ram
[For example, nickel sulfate, rII9I61tin sulfur] is used alone, or a mixed water bath solution of the above salts is used, and if necessary, a pH buffer, a pH buffer,
Baths with added antioxidants or stabilizers are used. Direct current, alternating current, pulsed current, etc. are used as the electrolytic waveform.

The film after treatment is gray, bronze, blue,
It develops a color such as green or reddish-purple, and these colors can be arbitrarily selected by changing the composition of the electrolytic solution and the electrolytic conditions. jl! After completing the three steps, the film is preferably subjected to a pore sealing treatment using boiled water, steam, etc., or painted as necessary.

In this way, in the present invention, aluminum and aluminum alloys can be colored in any color such as blue, green, red, etc., so when aluminum or aluminum alloys are used as building materials, the appearance can be improved. Moreover, the uses of those materials can be expanded. In the present invention, only a dipping treatment is performed during film modification in the second step, but it is also contemplated that an electrolytic treatment may be performed during film modification separately from the present invention.

However, when the electrolytic treatment method is adopted, electrical equipment is required, and of course electricity costs are also required, resulting in high manufacturing costs (
Become. Furthermore, there is a possibility that there will be a difference in the modified state between the part close to the electrode and the part far away, and the coloring state after the third step will be uneven, resulting in loss of commercial value. On the other hand, in the present invention, since electrolytic treatment is not performed during reforming, equipment costs and manufacturing costs are reduced. That is, for example, as a processing step @
If the washing bath after the completion of the first step is used as an acidic bath for the second step, the conventional treatment steps can be used as is.

In addition, color unevenness caused by a difference in distance between electrodes during electrolytic treatment is less likely to occur in dipping treatment.

Furthermore, even when processing materials with complex shapes, it is possible to achieve a finish with a uniform color tone by using effective stirring.

Example 1 First step electrolyte composition Sulfur II? 15W (weight)/V(
Volume) % Liquid temperature -20°C Current density/time I A/dm" x 30 minutes Film thickness 9μ 2nd step acidic bath composition Phosphorus $501711 Liquid temperature 20
°C Immersion time 5 minutes Stirring Liquid circulation Stirring voltage DC -15V Electrolysis time and coloring state corresponding to each electrolysis time Example 2 1J1 step, 2nd step...Same as Example 1.

Third step Voltage AC 10V Example 3 gJ1 step: Same as Example 1.

1J2 process liquid temperature 20℃ Immersion time 3 minutes Stirring Air stirring 3rd process energizing conditions DC, +10VX for 3 seconds and -15VX
Number of alternating energization repetitions of 10 seconds and coloring state Example 4 Liquid temperature 20°C Current density/time 1.5 A/dm'X30 film thickness 12μ 2nd step acidic bath composition Nitric acid so fil liquid temperature 20
°C Immersion time 10 minutes Third step electrolytic coloring solution composition Same as Example 2 - Solution voltage
AC 12V Example 5 First step: Same as Example 1.

9J2 process acidic bath composition 40171 bath temperature
30℃ Immersion time 1 minute Stirring 45KHz ultrasonic 3rd step electrolysis voltage AC 12V

Claims (1)

[Claims] In the first step, an anodic oxide film is formed on the aluminum or aluminum alloy material in an electrolyte mainly containing sulfuric acid, and then in the second step, it is immersed in an acid bath to remove the anodic oxide film formed in the first step. After the modification, in the third step, the film is electrolytically colored with an electrolytic coloring solution mainly containing metal salts such as nickel sulfate and stannous sulfate using direct current, alternating current, or pulsed current. The gray color, bronze color, pull discoloration method.