JPS59190389A - Method for coloring aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To form a colored film with superior corrosion resistance and wear resistance by subjecting Al having a formed anodic oxide film to anodic oxidation, AC electrolysis and anodizing and by carrying out electrolytic coloring in an aqueous soln. contg. a metallic salt. CONSTITUTION:Al or an Al alloy having an anodic oxide film formed in an aqueous soln. of sulfuric acid is anodized in an aqueous soln. forming a barrier film so as to homogenize a formed barrier layer, and the anodic oxide film is made microporous by AC electrolysis in an aqueous soln. contg. one or more among sulfuric acid, nitric acid, oxalic acid, sulfamic acid and ammonium hydrogensulfate. Anodizing is further carried out to improve the throwing power A desired colored film is then formed by electrolytic coloring in a bath contg. a metallic salt such as a salt of Ni, Co, Sn or Cu in accordance with the color tone to be provided.

Description

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

Conventionally, after applying an anodized film to aluminum, if electrolytic treatment is performed in an aqueous solution containing a metal salt, various colored films can be obtained depending on the type of metal salt in the "Asada method" and " It is well known as the ``Sumikaification Law''. However,
In these coloring methods, the metal particles are deposited unevenly in the pores of the anodic oxide film, so the resulting color tone is mostly gold, bronze, or black, and the colored film is colored in bright primary colors. difficult to obtain.

As a method for obtaining a colored film in a primary color system by improving the above points, a method of electrolyzing aluminum after forming an anodic oxide film in a bath containing phosphoric acid or pyrophosphoric acid, and then performing electrolytic coloring (Japanese Patent Laid-Open No. 1983-1996) 22834 Publication) Alternatively, after forming an anodic oxide film on aluminum, anodic electrolysis is performed at an electrolytic voltage of 1 to 20 V in an aqueous solution containing an inorganic metal salt to make the barrier layer uniform, and then electrolytic coloring is performed. (Japanese Patent Publication No. 54-39250) is disclosed.

The coloring machine grooves of these methods uniformly deposit and distribute metal particles in the film pores due to the fine structure of the anodic oxide film or the homogenization of the barrier layer, so the wavelength distribution of scattered light is narrowed and visible. The colors become primary colors. However, when both of the above methods are actually used to color aluminum, the former method disclosed in JP-A No. 53-22834 has a very strong solubility of phosphoric acid and pyrophosphoric acid in the film, resulting in poor corrosion and wear resistance of the colored film. is inferior and has poor circulation. Furthermore, the latter method disclosed in Japanese Patent Publication No. 54-39250 had a problem in that a colored film in bright primary colors could not be obtained in the electrolytic coloring process.

As a result of many years of intensive research and experimentation on this point, the inventor of the present invention created an anodic oxide film on aluminum, then homogenized the barrier layer through a first anodic electrolytic treatment, and then (- The anodic oxide film is made into a fine structure by performing alternating current electrolytic treatment in a bath where the film solubility is not very strong, and then a second anodic electrolytic treatment is performed to improve the coverage. After completing the electrolytic treatment, we apply electrolytic coloring to achieve corrosion resistance,
We have succeeded in obtaining a colored film in a primary color system with clear tones that has good abrasion resistance and good coverage and is highly practical.

That is, in the case of the method of the present invention, aluminum, on which an anodic oxide film has been formed in advance in an aqueous solution of sulfuric acid, is first subjected to anodic electrolysis treatment in an aqueous solution that forms a barrier type film, and then colored with sulfuric acid, nitric acid, and oxalic acid. , AC electrolytic treatment in an aqueous solution containing one or more of sulfamic acid and ammonium hydrogen sulfate, followed by anodic electrolysis treatment in an aqueous solution that forms a barrier type film, and then electrolysis in an aqueous solution containing metal salts. Coloring is done according to the order of coloring.

Next, embodiments of the present invention and matters to be kept in mind when implementing the invention will be explained in detail for each step.

(Al anodic oxide film treatment process There are no special restrictions on the anodic oxide film treatment in this step; general-purpose aluminum sashes are subjected to anodic electrolysis in an aqueous solution containing sulfuric acid, and the method of the present invention also There is no difference from those methods.

(131 First anodic electrolytic treatment step The purpose of the treatment in this step is to make the AC electrolytic treatment in the next step fol uniform, the anodic oxide film treatment step tA) and the subsequent AC electrolytic treatment step. If this step fil is provided between step (C), the barrier layer will be homogenized, and the AC electrolysis treatment in the next step (at) can be made uniform.

The electrolytic bath in this step may be a commonly used barrier type film forming bath, such as a bath containing boric acid, ammonium borate, tartaric acid, citric acid, lactic acid, etc. The electrolytic conditions at that time are as follows: It is sufficient to carry out electrolysis at a voltage equal to or slightly higher than the voltage for a period of time for the current value to converge and stabilize, that is, for several tens of seconds to several minutes.

+01 AC electrolytic treatment step In this step, the purpose of this step is to further modify the barrier by performing AC electrolysis at a voltage below the generation voltage of the anodic oxide film, that is, to create a fine structure suitable for obtaining a colored film in a primary color system. That is. It is essential for the bath composition at that time to be an aqueous solution containing one or more of sulfuric acid, nitric sulfamic acid, and ammonium hydrogen sulfate in order to obtain a good microstructure.

Although it is not possible to set a firm limit on the processing conditions V in these baths, when used as a single bath, 50 to 1
50 '71), nitric acid from 5 to 20, oxalic acid and ammonium hydrogen sulfate from 20 to more, sulfamic acid from 100
% or more is appropriate, and the bath temperature is 20 to 7
The purpose of this step can be achieved by electrolyzing at 0° C. with an AC voltage of 2 to 12 V for several seconds to 10 minutes. Under these conditions, it is necessary to appropriately select the concentration, temperature, and time of the bath under conditions that can suppress the dissolution of the coating (λ), so as not to impair the corrosion resistance and abrasion resistance of the coating.

(D) Second anodic electrolytic treatment process This process is mainly aimed at improving the coverage when electrolytically coloring is performed next, and is used for aluminum shapes etc. without this process. When electrolytic coloring is applied, it is affected by its shape, and the voltage drop in the shielded shape part is larger than in the part facing the electrode plate, and the spread of primary color coloring is poor, so it is difficult to put it into practical use. It's difficult. However, if this step is performed before the electrolytic coloring step, the barrier layer in the part facing the electrode plate will be thicker than the shielding part of the object to be treated, and the electrical resistance in the part facing the electrode plate will be large, so the electrolytic This improves the spreadability of coloring.

In addition, in the case of electrolytic coloring using a DC cathode, for example, when an aqueous solution containing metal salts such as copper, tin, or cobalt is used, a large amount of metal particles may be deposited on the edges of the object to be treated. Although the rolling properties may be significantly deteriorated, this step has the effect of preventing the above-mentioned phenomenon from occurring and making it possible to color the product uniformly.

In addition, the treatment conditions for this step may be generally the same as those for the first anodic electrolysis treatment, and the electrolysis voltage at this time is the same as or slightly higher than that of the AC electrolysis treatment in the previous step for several seconds. If such a treatment is carried out, the coloring properties will be improved, the barrier layer will become thicker, and the corrosion resistance of the film will also be improved.

(5)) Electrolytic coloring process This process may be performed under the same conditions as the conventionally known so-called "electrolytic coloring", and depending on the color tone of the colored film to be obtained, nickel cobalt, tin, copper, etc. Electrolytic coloring may be performed by methods such as DC cathode electrolysis, AC electrolysis, and pulse electrolysis in a bath containing a metal salt.

In this way, if the above-mentioned series of treatments are carried out when electrolytically coloring aluminum, the problems of the conventional method can be solved at once, and vivid primary colors with corrosion resistance, abrasion resistance, and coverage that are good and have a practical color tone can be obtained. A colored film is obtained.

Below, six specific examples of this invention are listed, and
Samples obtained in Examples 1 to 4 and comparative samples 1 to 4
Although the results of corrosion resistance and abrasion resistance tests for each of No. 3 are shown below, the present invention is not necessarily limited to these Examples.

Example 1 Aluminum alloy (6
0635-T5) ') Extruded profile 0 = 25TV,
D = 24.27'ηi ηt was anodized in a bath with 150 g of sulfuric acid and a bath temperature of 20°C, with an aluminum l'lum as the counter electrode, at a current density of 2.0'/, for 30 minutes to form an anodized film on the surface. Formed.

Next, add 30 grams of tartaric acid, and use carbon as the counter electrode in a bath at room temperature.
Perform anodic electrolysis treatment at 5V for 60 seconds, and then apply sulfuric acid at 50~
After performing electrolytic treatment at an AC voltage of 9 cm in a bath with a bath temperature of 25°C, anodic electrolysis treatment was performed at a bath temperature of 30 g/l with tartaric acid and carbon as a counter electrode for 60 seconds at an electrolytic voltage of 15 V in a bath at room temperature.
Next, sulfuric acid cylinder] tin 25~, sulfuric acid 10%, carbon counter electrode in a bath at room temperature, current density 0.51/d, 1 at 71
When alternating current electrolytic coloring was carried out for 20 seconds, a colored film having good coverage and having the following color tone was obtained on both the A side and the third side.

Example 2 An aluminum alloy (
60638-T5) was subjected to the same anodic oxidation and anodic electrolytic treatment as in Example 1, and further treated with oxalic acid 50'! /
After electrolyzing sulfamic acid 50 in a bath with a bath temperature of 50°C at 1% with carbon as the electrode and 11 V AC, 3 ol of tartaric acid was applied, and with carbon as the counter electrode in a room temperature bath, anodic electrolysis treatment was performed at a voltage of 15 V for 60 seconds. When the electrolytic coloring treatment was carried out in the same manner as in Example 1, a colored film having the following color tone and good running properties was obtained on both the A side and the third side.

Example 3 Aluminum alloy C6 having the cross-sectional shape shown in the attached drawings
o63S-T5) was anodized in the same manner as in Example 1, and then subjected to anodic electrolytic treatment at a voltage of 35 V for 60 seconds in a bath containing 30% ammonium borate at room temperature, using carbon as the counter electrode, and further anodic oxidation with sulfamic acid. 100 ~, sulfuric acid 7 liters, subjected to AC electrolysis treatment at a voltage of 11 V with carbon as the counter electrode in a bath with a bath temperature of 45 °C, and then tartaric acid 30 'l'it
- When anodic electrolysis was carried out at a voltage of 15 V for 60 seconds in a bath at room temperature using carbon as the counter electrode, and then electrolytic coloring was carried out in the same manner as in Example 1, side A and side 3 had the following color tones. A colored film with good flexibility was obtained.

Example 4 Aluminum alloy (6
063S-T 5) was subjected to anodization in the same manner as in Example 1, and then subjected to anodic electrolytic treatment at a voltage of 20V for 60 seconds using carbon as a counter electrode in a room-temperature bath with ammonium borate at 30°C, and then oxalic acid. 50~, perform AC electrolysis treatment at a voltage of 7V using carbon as a counter electrode in a bath with a bath temperature of 45°C, then perform anodic electrolysis treatment at a voltage of 15V for 60 seconds using carbon as a counter electrode in a room temperature bath with 30 g of ammonium borate, Next, electrolytic coloring was applied in the same manner as in Example 1, and a colored film having good coverage and having the following color tone was obtained on both the A side and the third side.

Example 5 Aluminum plate (A 1100 F) 7ox7ox
1.5t'P with sulfuric acid 150'/1, bath temperature 2C1, counter electrode with aluminum, current density 1-2'4. ．． (−
Anodic oxidation was performed for 30 minutes to form an anodic oxide film on the surface. Next, anodic electrolysis treatment was carried out at a voltage of 15 V for 60 seconds using carbon as the counter electrode in a bath containing 30% boric acid at room temperature, and then a counter electrode was formed in a bath containing 50% oxalic acid 50' and sulfuric acid 4 at a bath temperature of 48°C. After being subjected to AC electrolysis treatment at a voltage of 6■ as carbon,
Anodic electrolysis treatment was performed in a bath containing 30 g/l of boric acid at room temperature, using carbon as a counter electrode, and a voltage of 15 V for 60 seconds. Next, AC electrolytic coloring was carried out at a voltage of 12 V for 30 seconds using a bath E trowel with nickel sulfate at 30°C and boric acid at 30°C at a bath temperature of 35°C for 30 seconds, and a colored film as shown below was obtained.

Example 6 An aluminum plate (A 1100F) was subjected to the same anodic oxidation coating treatment as in Example 5, and then treated with 3'O% tartaric acid.

Anodic electrolysis treatment was performed in a bath at room temperature using carbon as the counter electrode at a voltage of 25 V for 60 seconds, and then in sulfuric acid at 5 og/l and a bath temperature of 2.
After performing an intercurrent electrolytic treatment at a voltage of 9 V in a bath at 5° C. using carbon as a counter electrode, anodic electrolysis treatment is performed for 60 seconds at a voltage of 15 V in a bath at room temperature with tartaric acid at 30°C and carbon as a counter electrode. Next, electrolytic coloring was carried out in the same manner as in Example 5, and a colored film as shown below was obtained.

- Corrosion resistance and wear resistance test (a) Sample preparation method l) Comparative sample rJA polar acid pole number J theory = -Sulfur M l 5ob, 20°C,
2.0~dX 30 minutes hydration sealing treatment...am of pure water
Immersed in water for 25 minutes 2) Present sample The colored films obtained in Examples 1 to 4 were subjected to the same hydration sealing treatment as the comparative sample, and then used as samples for each test.

(b) Test results However, the Cath test was conducted for 48 hours.

It is clear from the above test results that the colored aluminum obtained by the method of the present invention has good corrosion resistance and wear resistance.

[Brief explanation of drawings]

The drawing is a cross-sectional view showing the cross-sectional shape of a sample used in an example of the method of the present invention. (F)...Extruded profile, (At (Bl...Colored surface of profile, tel fD)...Dimensions of profile

Claims (1)

[Claims] Aluminum or aluminum alloy on which an anodic oxide film has been previously formed in an aqueous solution of sulfuric acid is subjected to anodic electrolysis treatment in an aqueous solution that forms a barrier type film, and then one of sulfuric acid, nitric acid, ferric acid, sulfamic acid, and ammonium hydrogen sulfate or After AC electrolysis treatment in an aqueous solution containing two or more types,
Furthermore, the anode 'W!' is placed in an aqueous solution forming a barrier type film!
A method for electrolytically coloring aluminum or an aluminum alloy, which comprises dissolving and then electrolytically coloring aluminum or an aluminum alloy in an aqueous solution containing a metal salt.