JPS636638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for electrolytically coloring aluminum or an aluminum alloy (hereinafter referred to as aluminum material) to a gold color.

Prior Art In recent years, with the development of electrolytic coloring methods, the demand for aluminum materials has increased significantly in various fields such as building materials, ships, and vehicle materials. It has become a major factor, and it is also necessary to incorporate aesthetic sense into aspects such as corrosion resistance and weather resistance to increase the decorative effect. In particular, in the field of building materials such as sliding entrance doors and high-class terrace doors, the above-mentioned demands are strong, and there is a strong demand for aluminum materials with a gold-colored surface treatment.

Although many methods for coloring aluminum materials have been reported, the electrolytic coloring method is widely used because it has relatively good corrosion resistance and weather resistance, and has little color nonuniformity. However, when using this method, due to its color development mechanism, colors such as bronze, amber, and black are often monotonous and dark, and the colors that can be obtained are limited. Furthermore, the degree of coloring progress is still not satisfactory, and there are still areas to be improved from the viewpoint of energy saving, such as shortening the electrolysis time.

By the way, several methods for obtaining gold color using electrolytic coloring have been reported, but in all of them, the metals used were expensive or harmful, so there were problems in terms of mass production, bath management, and pollution. It was hot. In addition, many of the gold colors had poor weather resistance.

As part of the improvement of the color problem mentioned above in the electrolytic coloring method, an anodic oxide film was formed on aluminum material by direct current electrolysis in a sulfuric acid electrolyte, and then an anodic oxide film was formed by further alternating current electrolysis in a sulfuric acid bath. However, it is reported in JP-A-54-124841 that a gold-colored colored film was obtained by subsequent alternating current electrolysis in an electrolytic bath containing stannous sulfate.

However, in general, even after primary anodizing treatment using DC electrolysis and secondary anodization treatment using AC electrolysis, even if AC electrolysis is carried out in an electrolytic coloring bath containing ordinary tinnous salts, a glossy and pale color will appear. Only a yellow colored film can be obtained, and in order to obtain a gold colored film, it is difficult to control the electrolytic coloring bath, and it is difficult to electrolytically color a uniform gold color.

Background of the Invention In view of the above-mentioned circumstances, the present applicant has obtained satisfactory results in all aspects such as weather resistance, uniform coloration, economical efficiency, etc., and is capable of electrolytic coloring to a uniform and fixed gold color. The company has developed a new method and has already filed a series of patent applications (Japanese Patent Laid-Open No. 55-62197,
57-177496). In other words, these methods basically take an aluminum material that has been subjected to anodization treatment or secondary anodization treatment using AC electrolysis, and a stannous salt, which has sulfur atoms in its molecules, and gradually oxidizes it in a liquid. By performing alternating current electrolysis in an electrolytic coloring bath whose main component is a substance that releases the sulfur it contains (hereinafter referred to as a decomposable sulfur compound) by decomposing the compound into Sulfur ions supplied from the decomposable sulfur compound and tin ions from the stannous salt are adsorbed into the pores of the oxide film, or are precipitated as tin sulfide in the pores of the oxide film. It forms a gold colored film with good spinability and uniformity.

This method has the above-mentioned advantages and is considered to be an innovative method in that electrolytic coloring to a uniform, fixed gold color system is possible. but,
Although there are no problems in the initial stage of electrolytic coloring treatment, it has been found that the following problems occur with repeated use of the electrolytic coloring bath.

In other words, in addition to the main coloring components, stannous salts and decomposable sulfur compounds, being decomposed and fixed in the pores of the oxide film, there are also oxidation-reduction reactions caused by electricity, bath circulation, oxidation reactions caused by air when left, and bath temperature. Due to the increase, etc., coloration inhibiting factors are produced. For example, Sn ²⁺ supplied by the stannous salt is oxidized to become a coloring inhibitor of Sn ⁴⁺ , and a degradable sulfur compound is decomposed to become a coloring inhibitor of S ^2- . On the other hand, the above Sn ⁴⁺
and S ^2- are fixed in the oxide film pores and become a colored film forming factor for SnS ₂ and are consumed, but some of the SnS ₃
This is the combination of SnS ₂ (colored film forming factor) and S ^2-
(coloring inhibitory factor). In this way,
By repeatedly using the electrolytic coloring bath, the coloring inhibiting factor gradually accumulates. For this reason,
The degree of coloring gradually decreases, and in order to obtain a uniform colored film, it is necessary to lengthen the current application time. Furthermore, Sn ²⁺ released from the stannous salt and sulfur released from the degradable sulfur compound combine,
Forms insoluble fine particles (SS) such as SnS. this
As SS gradually accumulates, it lowers the conductivity of the bath and adversely affects the degree of coloring, and it also adheres to the surface of the product as smut, resulting in the so-called dusting phenomenon. As a result, this causes the washing water to become contaminated, and since SS is often around 1μ, it becomes difficult to filter, the filter gets clogged quickly, and cleaning must be done more frequently. Therefore, a problem has arisen in that the life of the electrolytic coloring bath is relatively short.

Purpose of the Invention Therefore, the purpose of the present invention is to suppress the generation of coloring inhibiting factors and insoluble fine particles in the electrolytic coloring method for gold color, and to produce a uniform and constant coloring that is stable for a long period of time and has an excellent degree of coloring. The object of the present invention is to provide a method for electrolytically coloring gold colors.

Structure of the Invention In order to solve the above-mentioned problems, the present inventors have discovered that a surfactant (alkanesulfonic acid or its salt, alkanolsulfone It has been discovered that by adding an acid or its salt), the formation of the coloring inhibiting factors and insoluble fine particles can be suppressed, and the adsorption of insoluble particles to the surface of the anodic oxide film can also be prevented, thereby improving the coloring properties caused by AC electrolysis. , which led to the completion of the present invention.

That is, the method for electrolytically coloring an aluminum material to give a gold color according to the present invention is to electrolytically color aluminum or aluminum alloy that has been subjected to anodization treatment or secondary anodization treatment by AC electrolysis in an electrolytic coloring bath containing a metal salt. Alternatively, an electrolytic coloring method using a current waveform with an equivalent effect is used, and the electrolytic coloring bath contains (a) a stannous salt and (b) a sulfur atom in the molecule, which gradually decomposes in the liquid. or (c) a surface active substance selected from the group consisting of alkanesulfonic acid or its salt and alkanolsulfonic acid or its salt. It is characterized by using an electrolytic coloring bath containing a coloring agent.

Aspects of the Invention To explain the present invention in detail, first, an aluminum material is subjected to treatments such as degreasing, etching, neutralization, water washing, and smut removal by conventional methods as necessary, and then treated with an inorganic or organic acid, such as sulfuric acid, Using oxalic acid, chromic acid, or the like as an electrolytic solution, anodization is performed according to a conventional method to form an anodic oxide film on the aluminum surface. For anodizing treatment, it is sufficient to carry out electrolytic treatment by using an aluminum material as an anode and applying a DC or AC voltage between it and a suitable counter electrode according to a conventional method. The conditions are also sufficient as usual.

The above anodized aluminum material is
After performing necessary treatments such as washing with water, the electrolytic coloring treatment according to the present invention is directly performed, or after the above-mentioned anodizing treatment (primary) by direct current electrolysis, a secondary anodizing treatment by alternating current electrolysis is performed. , perform electrolytic coloring treatment.

When carrying out this two-step anodizing treatment, a sulfuric acid bath is used for both the primary and secondary sulfuric acid baths, and the first sulfuric acid bath preferably contains sulfuric acid at a concentration of about 100 to 300 g/L, but other organic acids and Inorganic acids may also be added. A primary anodic oxide film with a thickness of about 9 to 13 microns is formed by the primary anodizing treatment. This secondary anodic oxidation treatment by AC electrolysis is not intended to produce a colored film, but in conjunction with the primary anodization treatment by DC electrolysis, an oxide film with a double film structure is produced. This secondary anodizing treatment increases the amount of tin and decomposable sulfur compounds adsorbed into the micropores of the anodized film in the next electrolytic coloring process, resulting in a reddish gold color. It has significance as a process for achieving a (ochre-based) color development. That is, in the case of only normal anodizing treatment, a colored film ranging from light gold color to deep gold color is formed by the electrolytic coloring treatment described below, but when the above two-step anodization treatment is performed, A colored film with a reddish gold color is formed, which is an intermediate color between bronze and gold. Due to the dissociation reaction caused by alternating current electrolysis in this second sulfuric acid bath, the oxide film contains a large amount of sulfur and sulfur compounds, which forms metal sulfides in the next electrolytic coloring process, giving it a reddish tint. It is thought that a colored film with a tinged gold color is formed.

Furthermore, according to the present invention, by immersing the aluminum material in the bath for a while after the secondary anodizing treatment, the coloring property can be significantly improved even after immersion for a short time, and the deterioration in performance can be suppressed to a minimum. It was discovered that. It is the same as before that the coloring property can be improved by increasing the immersion time, but
In terms of productivity and film performance, the immersion time should be at least 1 minute.
Within 15 minutes, preferably 3 to 10 minutes.

The concentration of sulfuric acid in the second sulfuric acid bath is 100 to 280g/
, preferably 150 to 200 g/, more preferably 170 to 190 g/. At a high concentration of 280g/or more, the oxide film peels off, while at a concentration of 100g/
If the concentration is lower than that, the degree of coloring in the next electrolytic coloring step will decrease, which is not preferable. Further, the bath temperature is 10 to 30°C, preferably 15 to 25°C, and more preferably 18 to 23°C. At a high temperature of 30° C. or higher, peeling of the oxide film or powder blowing occurs as described above, while at a low temperature of 10° C. or lower, the degree of coloring decreases, which is not preferable. As for the electrolytic conditions, the current density is 0.5
-3A/ ^dm2 , preferably 1.0-2.5A/ ^dm2 , more preferably 1.5-2.2A/ ^dm2 . At high current density, the degree of coloring decreases, while at low current density, color unevenness, color loss, etc. occur, so it is preferable to set it within the above range. Also, the electrolysis time is 3 to 15
minutes, preferably 5 to 12 minutes. If the current application time is long, the oxide film becomes brittle, whereas if the current application time is short, the degree of coloring decreases, so it is preferable to set it within the above range.

Note that the same sulfuric acid bath can be used as the first sulfuric acid bath and the second sulfuric acid bath. That is, after primary anodization treatment is performed by direct current electrolysis in a sulfuric acid bath with the above-mentioned sulfuric acid concentration according to a conventional method, secondary anodization treatment is subsequently performed by alternating current electrolysis in the same sulfuric acid bath under the above-mentioned electrolytic conditions. It's okay to get old.

Furthermore, titanium sulfate may be added to the second sulfuric acid bath in order to increase the degree of coloring progress in the electrolytic coloring step and to generate a dark ocher colored film. Titanium sulfate includes primary titanium sulfate and secondary titanium sulfate, both of which can be used. The ionization voltage of titanium ions generated by the dissociation reaction by alternating current electrolysis in the secondary sulfuric acid bath containing titanium sulfate is higher than the ionization voltage of aluminum, so titanium ions act as an ionization promoter for aluminum, and as a result, It exhibits a film-thickening effect, and an AC oxide film can be obtained in a short time. Furthermore, sulfate ions increase in the solution, and the oxide film contains a large amount of sulfur and sulfur compounds, which increases the degree of coloring in the next electrolytic coloring process, resulting in a dark colored film. This is considered to be one of the factors that can lead to the formation of

Solutions of titanium sulfate with a concentration of 25% or more are commercially available, and can be used in the present invention. Titanium sulfate solution in the second sulfuric acid bath (commercially available 25
%up) concentration is 5-100ml/, preferably 10
~50ml/. If the concentration is high, the sulfuric acid bath becomes cloudy and precipitates are generated, whereas if the concentration is low, no increase in the degree of coloring progress can be expected, so the concentration is used within the above range. The electrolysis conditions, bath temperature, etc. are the same as in the case of the second sulfuric acid bath that does not contain titanium sulfate.

As described above, aluminum materials that have been anodized by direct current electrolysis or alternating current electrolysis in accordance with a conventional method, or are further placed in a second sulfuric acid bath or a second sulfuric acid bath containing titanium sulfate after primary anodization treatment by direct current electrolysis. The aluminum material that has been subjected to secondary anodizing treatment by AC electrolysis is then treated with a stannous salt, a decomposable sulfur compound, an alkanesulfonic acid or its salt, and an alkanolsulfonic acid or its salt selected from the group consisting of Electrolytic coloring is carried out by performing alternating current electrolysis in an electrolytic coloring bath containing at least one type of surfactant.

Examples of stannous salts that are one of the main components of the electrolyte used in the present invention include stannous sulfate, stannous oxalate, and stannous chloride. Any material that provides ions will suffice.

The concentration of the stannous salt is 0.3 g/(approximately 0.55 g as stannous sulfate) as the amount of stannous component in the salt.
g/(0.55×Sn/SnSO ₄ ≒0.3), which is about 0.5 g/ as stannous chloride), preferably considering the cost, the amount of the stannous component is
1.0~20g/(approximately 1.8~35 as stannous sulfate)
g/).

“Degradable sulfur compounds” include thiosulfuric acid,
Thiourea, thionyl chloride, thioglycolic acid, thiocyanic acid, thioacetic acid, thiocarbamic acid, etc.
Sulfoxylic acid, dithionite, sulfurous acid, pyrosulfuric acid, pyrosulfite, dithionic acid, trithionic acid, excluding those belonging to thio compounds such as sulfuric acid and its salts such as sodium, potassium, ammonium, etc. Tetrathionic acid, pentathionic acid,
These include sulfur oxyacids such as hexathionic acid or their sodium, potassium, and ammonium salts, and sulfur halides such as sulfur dichloride and sulfur monobromide.

The concentration of the “degradable sulfur compound” is approximately 0.08 g/(as thioglycolic acid HSCH ₂ COOH) the amount of sulfur component in its molecule.
(0.25×S/HSCH ₂ COOH≒0.08)) or more,
Preferably the amount of sulfur component in the molecule is 0.12~
15g/approx. (thioglycolic acid HSCH ₂ COOH
about 0.43 to 54 g/).

In addition to the above-mentioned components, the electrolytic coloring bath according to the present invention also contains Sn ⁴⁺ , which is produced by oxidation-reduction reactions caused by energization, circulation of the bath, oxidation reactions during standing, etc.
Among coloring inhibiting factors such as S ^2- and insoluble fine particles,
Alkanesulfonic acid or its salt, alkanolsulfonic acid or its salt, which acts as a surfactant, is used to suppress the dissolution of Sn ⁴⁺ and S ^2- in the liquid and to suppress the dispersion of insoluble fine particles in the liquid. One or more of these can be added. Examples of alkanesulfonic acids or salts thereof include sodium alkanesulfonate, tin alkanesulfonate, nickel alkanesulfonate, lead alkanesulfonate, zinc alkanesulfonate, silver alkanesulfonate, etc.
Examples of the alkanolsulfonic acid or its salt include sodium alkanolsulfonate, tin alkanolsulfonate, nickel alkanolsulfonate, lead alkanolsulfonate, zinc alkanolsulfonate, and silver alkanolsulfonate. These surfactants are added at a rate of 2 to 40 g/, preferably 5 to 20 g/.

The three components mentioned above are always added to the electrolytic solution as essential components, but an electrolyte component is usually added to impart conductivity, and a stannous antioxidant may also be added.

Electrolytes for imparting electrical conductivity include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, and chromic acid, which are usually used in electrolytic coloring, as well as oxalic acid, acetic acid, propionic acid, formic acid, tartaric acid, and citric acid. Examples include organic acids such as acids, their ammonium salts, amino salts, and imino salts, and an aqueous solution of these is used as an electrolyte and the above-mentioned compounds are added thereto to form an electrolytic coloring bath. In addition, salts of the above-mentioned inorganic or organic acids of metals such as lithium, sodium, potassium, magnesium, and aluminum, which do not participate in color development, can also be added as electrolytes. The concentration of these electrolytes added is about 3 g/or more,
Preferably it is about 5 g/or more (up to the saturation point).

Adding an antioxidant to prevent the oxidation of stannous to stannic is useful because tin salts are expensive and the bath concentration remains constant. Examples of antioxidants include strong reducing substances such as hydrazine (hydrazine sulfate), hydroquinone, resorcinol, hydroxylamine, and cresol sulfonic acid, L-ascorbic acid, ferrous salts of inorganic or organic acids, formalin, etc. There are weakly reducing substances such as The stronger the reducing property, the more suppressed the generation of stannic tin, but as the amount added increases, the color becomes lighter, and when the amount is about 5 g/or more, it becomes almost uncolored. On the other hand, even with weakly reducing formalin, the color becomes slightly lighter, but with L-ascorbic acid, ferrous salts of inorganic acids, or organic acids, there is no change in density or color tone at all. Therefore, when adding antioxidants, weakly reducing substances, especially L-ascorbic acid and ferrous salts, are preferred, while strongly reducing substances should be used in an amount of 5 g/or less.

The anodic oxide film electrolytically colored as described above is subjected to a sealing treatment using boiling water, chemicals, pressurized steam, or the like, if necessary. Further, after performing this sealing treatment, or without performing the sealing treatment, the surface may be further protected by dip coating or electrodeposition coating with a resin paint, if necessary.

The aluminum material colored by the method of the present invention is pure aluminum or pure aluminum containing one or more metals such as silicon, magnesium, copper, nickel, zinc, chromium, lead, bismuth, iron, titanium, and manganese. It is an alloy.

Effects and Effects of the Invention According to the present invention, by adding alkanesulfonic acid or its salt, or alkanolsulfonic acid or its salt, which acts as a surfactant, to the electrolytic coloring bath, a colored film forming factor is added. Coloration inhibiting factors such as Sn ⁴⁺ , S ^2- , and insoluble fine particles, which originate from stannous salts and degradable sulfur compounds, are produced by oxidation-reduction reactions caused by electricity, circulation of baths, and oxidation reactions when left standing. Among them, the dissolution of Sn ⁴⁺ and S ^2- into the electrolyte is suppressed, and the dispersion of insoluble fine particles into the liquid is suppressed (the dispersibility of insoluble particles deteriorates, making them easier to settle and separate). This improves the coloring property of alternating current electrolysis, shortens the coloring energization time, extends the life of the electrolytic coloring bath, greatly reduces coloring variations, and enables the formation of a stable, uniform colored film over a long period of time. becomes. Also,
Insoluble fine particles tend to settle relatively easily and their amount in the bath decreases, which not only improves the degree of coloring, but also greatly reduces the adhesion of insoluble fine particles to products, improving cleaning performance. It is possible to form a beautiful colored film.

According to the electrolytic coloring method according to the present invention, a colored film that is stable and uniform for a long period of time and has excellent corrosion resistance and weather resistance is formed. In addition, the color tone varies from pale gold to deep gold in the case of normal anodizing treatment, while in the case of two-step anodizing treatment, it becomes a reddish gold color. Depending on the selection of the electrolytic coloring bath or the concentration of each component in the electrolytic coloring bath, a gold-colored colored film of any tone can be formed. By the way, the precipitates produced by the conventional alternating current electrolytic coloring method in a tin bath are presumed to be metallic tin, tin oxide, or reduced tin hydroxide, whereas in the method of the present invention, "degradable" It is thought that a large amount of tin sulfide is produced by the sulfur supplied from the sulfur compound, and the color (gold) of this tin sulfide is added to give the appearance of a gold color. Furthermore, when a two-stage anodizing treatment is adopted, the gloss of the colored film on the aluminum material decreases, and the reddish tinge is reduced, along with the effect of the secondary anodizing treatment by AC electrolysis in the second sulfuric acid bath. It is thought to have a gold color tone close to ocher with a woody texture.

In addition, the decomposable sulfur compound contained in the electrolytic coloring bath has the effect of improving the coloring property, especially when the alternating current electrolysis in the secondary sulfuric acid bath (particularly the secondary sulfuric acid bath containing titanium sulfate) is applied. Coupled with the effect of secondary anodizing treatment, the rate of coloring progresses extremely well, so electrolytic coloring can be done in a short time, and even on shapes with complex shapes, a gold-colored colored film is produced uniformly. can be formed.

Therefore, it can be said that the electrolytic coloring method of the present invention is extremely practical from the viewpoint of productivity, workability, bath management, and quality, as well as from the user's needs for gold coloring.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 and Comparative Example 1 Extruded aluminum profile A-6063S (150L×
A current density of 1.0 A/dm ² was applied between the anode and the aluminum cathode provided as the counter electrode.
Direct current electrolysis was carried out for 35 minutes to form a 9 μm anodic oxide film on the surface of the extruded aluminum profile. After washing it with water, put it in a tank of 400L x 100W x 150Hmm
It was immersed in the prepared electrolytic coloring solutions A (Example 1) and B (Comparative Example 1) having the following compositions, and a voltage of 9 V was applied between the electrodes and a carbon electrode provided as a counter electrode with a distance between the electrodes of 250 mm.
AC electrolysis was carried out for 8 minutes.

When each electrolytic coloring solution was set at 18 to 20℃ and the above operations were performed continuously for 10 days, electrolytic coloring solution B
When using (Comparative Example 1), a dark gold colored film was obtained on the first day, but a pale gold colored film was obtained on the 10th day, and the colorability decreased and , smut was adhered to the colored film of the extruded aluminum profile. On the other hand, when electrolytic coloring solution A was used (Example 1), a dark gold-colored colored film with almost the same color tone was formed on the first day and the tenth day. Moreover, no adhesion of smut was observed on the colored film on the 10th day.

Electrolytic coloring liquid A: Stannous sulfate g / Sulfuric acid 40g / Sodium trithionate 1.2g / Formalin 2g / Alkanesulfonic acid 10g / Electrolytic coloring liquid B: Stannous sulfate 6g / Sulfuric acid 40g / Sodium trithionate 1.2 g/Formalin 2g/Example 2 and Comparative Example 2 Extruded aluminum profile A-6063S (150L x
A current density of 1.0 A/dm ² was applied between the anode and the aluminum cathode provided as the counter electrode.
Direct current electrolysis was carried out for 35 minutes to form a 9 μm anodic oxide film on the surface of the extruded aluminum profile. After washing this with water, using carbon as the counter electrode, sulfuric acid 18W/
V%, immersed in a 20°C solution at a current density of 2A/ ^dm2.
AC electrolysis was further performed for 10 minutes.

After washing the aluminum extruded shape that underwent the above treatment, it was immersed in electrolytic solutions A (Example 2) and B (Comparative Example 2) with the following composition prepared in 5 baths of 400 L x 100 W x 150 H mm, and provided as a counter electrode. AC electrolysis was carried out at 9V for 8 minutes with a distance between the electrodes of 250 mm.

When each electrolytic coloring solution was set at 18 to 20℃ and the above operations were performed for 10 consecutive days, it was found that when electrolytic coloring solution B was used (comparative example 2), on the first day A dark ocher-colored film was obtained, but on the 10th day it became a relatively light ocher-colored film, the colorability decreased, and smuts were attached to the colored film of the aluminum extrusion. . On the other hand, when electrolytic coloring solution A was used (Example 2), a dark ocher colored film with almost the same color tone was formed on the first day and the tenth day. Moreover, no adhesion of smut was observed on the colored film on the 10th day.

Electrolytic coloring solution A: Stannous sulfate 6g / Sulfuric acid 40g / Sodium trithionate 1.2g / Formalin 2g / Alkanesulfonic acid 10g / Electrolytic coloring solution B: Stannous sulfate 6g / Sulfuric acid 40g / Sodium trithionate 1.2 g/Formalin 2g/Example 3 and Comparative Example 3 Processed in exactly the same manner as in Example 1 except that electrolytic coloring solutions A (Example 3) and B (Comparative Example 3) having the following compositions were used as electrolytic coloring solutions. However, when electrolytic coloring solution B was used (comparative example 3), a dark gold-colored colored film was obtained on the first day, but on the 10th day.
On the second day, the colored film became a pale gold color, and the colorability decreased, and smut was attached to the colored film on the extruded aluminum profile. On the other hand, when electrolytic coloring solution A is used (Example 3), the first
A gold colored film with almost the same tone was formed on the 10th day and the 10th day. Moreover, no adhesion of smut was observed on the colored film on the 10th day.

Electrolytic coloring solution A: Stannous sulfate 6g / Sulfuric acid 40g / Sodium trithionate 1.2g / Formalin 2g / Alkanolsulfonic acid 10g / Electrolytic coloring solution B: Stannous sulfate 6g / Sulfuric acid 40g / Sodium trithionate 1.2 g/Formalin 2g/Example 4 and Comparative Example 4 Processed in exactly the same manner as Example 1 except that electrolytic coloring solutions A (Example 4) and B (Comparative Example 4) having the following compositions were used as electrolytic coloring solutions. However, when electrolytic coloring solution B was used (Comparative Example 4), a dark gold-colored colored film was obtained on the first day, but on the 10th day.
On the second day, a pale gold-colored colored film was formed, the colorability was decreased, and smut was attached to the colored film of the aluminum extruded shape. On the other hand, when electrolytic coloring solution A is used (Example 4), the first
On the 10th day and on the 10th day, a dark gold colored film with almost the same tone was formed. Moreover, no adhesion of smut was observed on the colored film on the 10th day.

Electrolytic coloring liquid A: Stannous sulfate 4g/ Sulfuric acid 40g/ Sodium trithionate 1.2g/ Tin alkanol sulfonate 13.3g/ Electrolytic coloring liquid B: Stannous sulfate 5g/ Sulfuric acid 40g/ Sodium trithionate 1.2g/

Claims (1)

[Claims] 1. A method of electrolytically coloring aluminum or aluminum alloy that has been subjected to anodization treatment or secondary anodization treatment by alternating current electrolysis in an electrolytic coloring bath containing a metal salt using alternating current or a current waveform having an equivalent effect, The electrolytic coloring bath contains (a) a stannous salt and (b) a sulfur atom in the molecule, which is gradually decomposed in the solution or decomposed by an oxidation-reduction reaction caused by alternating current. Aluminum or aluminum characterized by using an electrolytic coloring bath containing a substance that releases sulfur and (c) a surfactant selected from the group consisting of alkanesulfonic acid or its salt and alkanolsulfonic acid or its salt. Gold color electrolytic coloring method for alloys.