JPS59190390A - Method for coloring aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To form a colored film of a clear color tone with superior corrosion resistance and wear resistance by subjecting the surface of specified Al to anodic oxidation, AC electrolysis and anodizing and by carrying out electrolytic coloring in an aqueous soln. contg. a metallic salt. CONSTITUTION:Al of >=99.0% purity or an Al alloy having the composition of JIS alloy No.6063 and subjected to no artificial aging is anodically oxidized in an aqueous soln. of sulfuric acid to form an anodic oxide film on the surface. The anodic oxide film is made microporous by AC electrolysis in an aqueous soln. contg. one or more among sulfuric acid, nitric acid, sulfamic acid and ammonium hydrogensulfate, and anodizing is carried out in an aqueous soln. forming a barrier film 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 aluminum alloys, and its purpose is to impart corrosion resistance, wear resistance, and clingability to the surface of aluminum (including aluminum alloys). To obtain a colored film in a primary color system with a clear color tone and rich in practicality.

Conventionally, after applying an anode and oxide film to aluminum, electrolytic treatment is performed in an aqueous solution containing a metal salt, and various colored films can be obtained depending on the type of metal salt in the bath. This is known as the "Asada method". It is also known as the ``Sumikaification Law.'' However, with these coloring methods, metal particles are deposited unevenly in the pores of the anodic oxide film, so the resulting colors are mostly gold, bronze, and black, and are not bright primary colors. It is difficult to obtain a colored film.

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 anodized film in a bath containing phosphoric acid or pyrophosphoric acid, and then performing electrolytic coloring (
(Japanese Unexamined Patent Publication No. 53-22834), or 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. , a method of electrolytic coloring (Japanese Patent Publication No. 54-39250) has been disclosed.

The coloring mechanism of these methods is that metal particles are uniformly precipitated and dispersed in the film pores due to the fine structure of the anodic oxide film or the homogenization of the barrier layer, which narrows the wavelength distribution of scattered light and makes it visible. The colors are 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 ability to move around. However, the latter method disclosed in Japanese Patent Publication No. 54-39250 had a drawback in that it was not possible to obtain a colored film in bright primary colors during the electrolytic coloring process.

As a result of extensive research and experiments over many years on this point, the inventor of the present invention used aluminum with a specific aluminum composition or an aluminum alloy with a specific alloy composition and history as a workpiece, and applied anodization treatment to the workpiece. The anodic oxide film is then subjected to alternating current electrolysis treatment in a bath where the solubility of the film is not very strong to create a fine structure of the anodic oxide film. By performing this treatment, we aim to improve the stickiness and turnability, and after completing this series of electrolytic treatments, we
By applying the coloring method, we have succeeded in obtaining a colored film in a clear primary color system, which has good corrosion resistance, abrasion resistance, and coverage, and is highly practical.

That is, in the case of the method of the present invention, there are nine types of aluminum to be colored. Using aluminum with a purity of 0% or more, or an aluminum alloy with a composition of Japanese Industrial Standards alloy number 6063 and not subjected to artificial aging treatment,
This is anodized in an aqueous solution of sulfuric acid to form a highly oxidized film on the surface, and then subjected to alternating current electrolysis treatment in an aqueous solution containing one or more of sulfuric acid, nitric acid, nulfamino acids, and ammonium hydrogen sulfate. The method is characterized in that it is further subjected to an anodic electrolytic treatment in an aqueous solution that forms a barrier type film, and then electrolytically colored in an aqueous solution containing a metal salt.

Next, we will explain in detail the embodiments of this invention and the matters to be kept in mind when implementing them for each step, but first, we will explain the reason why we specified the composition and history of aluminum and aluminum alloys that are subject to coloring. The main reason why the types of aluminum and aluminum alloys are specified in the present invention is to uniformize the formation of a porous film by anodizing treatment.

It is well known that a porous film is formed when general aluminum or aluminum alloy is anodized in an aqueous solution such as sulfuric acid, but depending on the purity and composition of the aluminum, the pore size and barrier layer of the anodized film may be uneven. occurs. Even if the method of the present invention is applied to such a non-uniform anodic oxide film, it is difficult to obtain a good primary color colored film. For this reason, the present inventor has developed various aluminum +? - Numerous trials fI for aluminum and aluminum alloys! As a result of repeating one mistake and searching for the optimal material that would yield a colored film in vivid primary colors, we found that aluminum with a purity of 99.0% or higher had a uniform pore size and barrier layer in the anodic oxide film, resulting in the invention of the present invention. The method can be fully implemented, and it is still possible to use alloy number 6 of the Japanese Industrial Standards, which is used for applications such as aluminum sash.
It has been discovered that even with an aluminum alloy having a composition of 063, if it is not subjected to artificial aging treatment, the pore diameter of the anodic oxide film and the barrier layer become uniform, and the method of the present invention can be carried out. However, when the aluminum alloy is artificially aged and frozen, precipitation of solute atoms, that is, precipitation of an intermetallic compound of magnesium and silicon, occurs, resulting in non-uniformity in the pore size of the porous film and the barrier layer.

(8. Anodic oxide film treatment step) The anodic oxide film treatment in this step has no special restrictions on the treatment process itself, as long as the above-mentioned specific aluminum or aluminum alloy is used as the material to be treated, and general-purpose aluminum sash etc. The method of the present invention, in which anodic electrolysis is carried out in an aqueous solution containing sulfuric acid, is no different from those methods.

(c) AC electrolytic treatment step In this step, alternating current electrolysis is performed at a voltage lower than the generation voltage of the anodic oxide film to further modify the barrier, that is, to create a fine structure suitable for obtaining a colored film in primary colors. The purpose is to The bath composition at that time was sulfuric acid, nitric acid,
An aqueous solution containing one or more of sulfamic acid and ammonium hydrogen sulfate is an essential requirement for obtaining a good microstructure.

Although no definite limitations can be placed on the treatment conditions in these baths, when used as a single bath, sulfuric acid has a
0'/1, nitric acid 5-20%, oxalic acid and ammonium hydrogen sulfate 20f/1 or more, sulfamic acid 100'/1
2 or more is appropriate, and the bath temperature is 20-70
The purpose of this process can be achieved by electrolyzing at AC voltage of 2 to 12 V for several seconds to 10 minutes.Then, by appropriately selecting the concentration, temperature, and time of the bath under these conditions, the film can be formed. It is necessary to carry out the process under conditions that can suppress the dissolution of the coating so as not to impair the corrosion resistance and abrasion resistance of the coating.

(q Anodic electrolytic treatment process This process is mainly intended to improve the coverage when electrolytically coloring is performed next, and it is possible to electrolytically color aluminum shapes etc. without applying this process. In this case, due to the influence of the shape, the voltage drop in the shielded portion becomes larger than that in the portion facing the electrode plate, and the coverage of primary coloring becomes poor, making it difficult to put it into practical use. However, if this step is performed before the electrolytic coloring step, the barrier layer of the part facing the electrode plate will be thicker than the shielding part of the object to be treated, and the electrical resistance of the part facing the electrode plate will increase. This improves the spreadability of electrolytic 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. However, it may significantly worsen maneuverability.

Providing this step has the effect of preventing the occurrence of the above-mentioned phenomenon and uniformly coloring the product.

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. It is sufficient to carry out the treatment for a few seconds at a voltage equal to or slightly higher than that of electrolytic treatment, and when such a treatment is carried out, the colorability is improved, the barrier layer becomes thicker, and the corrosion resistance of the film is also improved.

(To) 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 direct current cathode electrolysis, alternating current electrolysis, and pulse electrolysis in a liquid containing a metal salt.

In this way, if the above-mentioned series of treatments are carried out when coloring aluminum or aluminum alloy, the problems of the conventional method can be solved at once, and the product has good corrosion resistance, abrasion resistance, and gripability, and is highly practical. A colored film with clear primary colors can be obtained.

Hereinafter, we will list five examples of the present invention and a comparative example to demonstrate the influence of the presence or absence of artificial aging treatment.
The results of corrosion resistance and abrasion resistance tests for the samples obtained in Examples 1 to 3 and Comparative Samples 1 to 3 will be posted, but the present invention is not necessarily limited to these Examples. .

Example 1 Aluminum alloy (60638) having the cross-sectional shape shown in the attached drawings and not subjected to artificial aging treatment +7) Extruded section G = 25”d, D = 24.2”7J Mte 1
5o117. , in a bath with a bath temperature of 20'Q and a current density of 1.2 to . ,/, 30 minutes of @polarity treatment was performed to form an anodic resistant film on the surface. Next is sulfuric acid 15c! ! /l, bath temperature 30'0, AC voltage 3
Electrolytic treatment was carried out at 15 V, and further anodic electrolytic treatment was carried out at a voltage of 15 V for 60 seconds in a bath containing 30% tartaric acid at room temperature and using carbon as a counter electrode. After that, 5 parts of tin sulfate, 10 parts of sulfuric acid,
When DC electrolytic coloring was carried out in a room temperature bath at a voltage of 12 V using carbon as an anode, a colored film with good coverage and good coverage was obtained on both sides A and B.

Example 2 An extruded aluminum alloy (60638) having the cross-sectional shape shown in the attached drawings and not subjected to artificial aging treatment was subjected to the same anodic oxidation treatment as in Example 1, and further treated with 50% oxalic acid,
After performing electrolytic treatment using 50% sulfamic acid in a bath with a bath temperature of 45°C and using carbon as the counter electrode at an AC voltage of 3 cm, electrolyzing with 30% tartaric acid and using carbon as the counter electrode in a bath at room temperature at a voltage of 15 V for 60 seconds. When anodic electrolytic treatment was carried out and then electrolytic coloring was carried out in the same manner as in Example 1, a colored film having good coverage and having the following color tone on both the A side and B side was obtained.

Example 3 An anodized film similar to Example 1 was formed on an extruded aluminum alloy (60638) having the cross-sectional shape shown in the attached drawings and not subjected to artificial aging treatment, and then 150 J of sulfuric acid was applied.
'47, electrolytic treatment was performed for 30 seconds at an AC voltage of 3V using carbon as the counter electrode in a bath with a bath temperature of 30°C, and then an anodic electrolysis treatment was performed for 60 seconds at a voltage of 15V at room temperature using the following treatment solutions, and then When electrolytic coloring was carried out in the same manner as in Example 1, a colored film 5 with good spreading properties and having the following color tone on both sides A and B was obtained.

Example 4 Aluminum plate with an aluminum composition of 99.0% or more (A
l1.0OP) 70X 70X 1.5 f m/m
was anodized in a sulfuric acid bath of 4215 o',i and a bath temperature of 20''C, using aluminum as the counter electrode, and a current density of 1.2 - 30 minutes for 30 minutes to form an anodized film on the surface. , sulfamic acid 50~.C, carbon counter electrode in a bath with a bath temperature of 48°C, carbon as a counter electrode, and boric acid 30~. After performing an anodic electrolysis treatment with a voltage of 15V and 60 seconds as a counter electrode with carbon in a bath at room temperature. Then, AC electrolytic coloring was performed in a bath of nickel sulfate 30 to boric acid 3ON at a voltage of 12 V for 30 seconds using nickel as the counter electrode, and a colored film as shown below was obtained.Example 5 Aluminum composition 99 .0% or more aluminum plate (A
IlooP) was subjected to the same anodizing treatment as in Example 4 to form an anodized film on the surface, and then subjected to alternating current electrolysis treatment at a voltage of 5 μm in a bath of sulfuric acid and a bath temperature of 25° C. with carbon as the counter electrode. After this, anodic electrolysis treatment was carried out using tartaric acid for 30 seconds in a bath at room temperature for 15V and 560 seconds using carbon as the counter electrode. Next, electrolytic coloring was carried out in the same manner as in Example 4, and a colored film as shown below was obtained.

Comparative Control Example In order to confirm the influence of the presence or absence of artificial aging treatment, three types of plates made of different materials were treated under the following conditions, and the results shown in the table below were obtained.

Anodic oxidation---1---Sulfuric acid 150'71420℃
, 1.2 immersions x 30 minutes AC electrolytic treatment bath
3 o 48°C anodizing bath - 111 - Sulfuric acid 150
g/1. Boric acid 30°C, 30°C corrosion resistance and abrasion resistance test (a) Sample preparation method 1) Comparative sample anodizing treatment - 1 - Sulfur hanging 150 & 73.20°C, 1
2Iyd Go , was used as the sample for each test.

(Rono test results However, the canine test was conducted for 16 hours.

From the above results, it is clear that the anodic electrolytic treatment and AC electrolytic treatment in the method of the present invention had no effect on corrosion resistance and wear resistance.

[Brief explanation of drawings]

The drawings are plane views showing the surface shapes of the samples used in the examples of the method of the present invention. (0. Form dimensional procedure amendment (voluntary) Otsu C;, to]. May 16, 1980, Mr. Kazuo Wakasugi, Commissioner of the Patent Office■, small case indication Patent Application No. 6507, 1988) ( ′
- No. 2, Title of the invention Method for coloring aluminum alloy for aluminum shavings 3, Relationship with the case of the person making the amendment Patent applicant 4, Agent Address: 930 (0764) 23-5
433S Target of amendment 1. Detailed explanation of the invention in the specification Contents of the amendment Page 17 of the specification, lines 4 to 5, ``Anodizing bath----150 monosulfuric acid 30% boric acid 30%
°C electrolytic coloring--111 AC 0.5~G x 30 seconds
"Anodizing --- monotartaric acid 30'J, 20" C110
V
Boric acid 30 years 30" C1 AC 0.5.4y x 30 seconds" - Corrected.

Claims (2)

[Claims] (1) Aluminum with an aluminum composition of 99.0% or more, or aluminum with a composition of Japanese Industrial Standard alloy number 6063 and not subjected to artificial aging treatment,
After anodizing in an aqueous solution of corrosion and acid to form an anodized film on Table M1, AC electrolysis treatment was performed in an aqueous solution containing 1% or more of sulfuric acid, nitric acid, nulfamic acid, and ammonium hydrogen sulfate. A method for electrolytically coloring aluminum or an aluminum alloy, which further comprises performing an anodic electrolytic treatment in an aqueous solution that forms a barrier type film, and then electrolytically coloring it in an aqueous solution containing a metal salt. (2) The method for coloring aluminum or aluminum alloy according to claim 1, wherein the final step of electrolytic coloring is direct current cathode electrolysis.