JPS6357511B2 - - Google Patents

Description

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

Conventional technology Many methods for coloring aluminum materials have been reported, but a typical method is a method in which the anodic oxide film of aluminum material is immersed in an organic dye or inorganic compound solution (dying method). ),
A method in which the film develops color during anodization using the alloy components of the aluminum alloy or electrolyte components during anodization (natural coloring method), and a method in which the anodic oxide film is electrolyzed with alternating current in a metal salt bath to convert the metal or metal oxide into an anode. A method of developing color by adsorption into the pores of an oxide film (electrolytic coloring method) is known.

Among these, the dyeing method has problems such as weather resistance and non-uniformity of color due to variations in bath temperature and film thickness.On the other hand, the natural coloring method has problems such as difficulty in obtaining an alloy with a uniform composition and There are problems such as uneven color due to variations in temperature, variations in bath temperature, etc., and high costs.

Therefore, the electrolytic coloring method is widely used because it has relatively excellent corrosion resistance and weather resistance, and less nonuniformity of color. 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.

As part of the improvement of the above-mentioned color problem in the electrolytic coloring method, an anodic oxide film was formed on the aluminum material by direct current electrolysis in a sulfuric acid electrolyte, and then DC electrolysis was performed again in a phosphoric acid or chromic acid bath to form the above-mentioned color problem. A method of forming a blue-colored film by modifying the porous layer near the barrier layer of the oxide film into a branched form and then subjecting it to alternating current electrolysis in an electrolytic bath containing metal salts was published in 1973. This is proposed in Publication No. 23658. Further, it is disclosed in Japanese Patent Application Laid-Open No. 124841/1983 that the porous layer near the barrier layer is modified into a branched shape by a combination of anodizing treatment using direct current electrolysis and anodizing treatment using alternating current electrolysis. In this publication, it is reported that a gold-colored colored film was obtained by performing alternating current electrolysis in an electrolytic bath containing stannous sulfate after the above treatment. Furthermore, the present applicant himself has proposed a method in which a gold-colored colored film can be obtained by carrying out alternating current electrolysis in an electrolytic bath containing a stannous salt after ordinary anodizing treatment.
(Japanese Patent Publication No. 54-23662 and Japanese Patent Application Laid-open No. 55-62197).

As described above, the colored film obtained by the conventional electrolytic coloring method has a dark color such as bronze color, and the colored film obtained by the above-mentioned improved methods has a gold color or blue color.

By the way, in recent years, with the involvement of electrolytic coloring method,
The demand for aluminum materials is increasing significantly in various fields such as building materials, ships, and vehicle materials, but the surface treatment of aluminum materials is not only corrosion-resistant, but also appearance is a major factor, and corrosion resistance, weather resistance, etc. It is also necessary to incorporate aesthetic sense into the perspective and increase the decorative effect. The above requirements are particularly strong when it comes to building materials such as sliding entrance doors and high-class terrace doors.

Therefore, especially in the area of building materials, users have pointed out that bronze coloring is too dark and gold coloring is too light, so there is a desire to develop a method that can form a colored film with a color intermediate between bronze and gold. For the formation of a colored film with an intermediate color between bronze and gold, Mn bath or Se
-Ag bath etc. have been considered, but in any case, it is within the range of yellow-gold color and it is not possible to obtain an intermediate color with a reddish subdued tone.

Problems to be Solved by the Invention Therefore, an object of the present invention is to provide an electrolytic coloring method capable of forming a colored film in a color intermediate between bronze and gold, that is, a reddish ocher color, on the surface of an aluminum material. It is in.

Still another object of the present invention is to provide an electrolytic coloring method that can achieve the above object and form a colored film with excellent corrosion resistance, weather resistance, spreadability, uniform coloration, etc. with good mass production.

Means for Solving the Problems As a result of intensive research by the present inventors, aluminum materials were anodized by direct current electrolysis in a first sulfuric acid bath, and then secondary anodized by alternating current electrolysis in a second sulfuric acid bath. After that, stannous salt,
Sulfuric acid, and substances that have sulfur atoms in their molecules and release the sulfur they contain by gradually decomposing in liquid or undergoing redox reactions by alternating current (hereinafter abbreviated as degradable sulfur compounds) ) in an electrolytic coloring bath containing as the main component, it was surprisingly possible to obtain a colored film with a reddish ocher color, which is an intermediate color between bronze and gold, unlike the gold color. This is the heading that led to the completion of the present invention.

Effect of the Invention After performing the anodizing treatment in the sulfuric acid bath of the present invention, that is, the primary anodizing treatment by direct current electrolysis and the secondary anodizing treatment by alternating current electrolysis, the electrolytic coloring bath containing a normal tinned salt is applied. Even if AC electrolysis is carried out inside,
Only a glossy pale yellow colored film is obtained.
On the other hand, even if AC electrolysis is carried out in an electrolytic coloring bath containing a stannous salt and the decomposable sulfur compound after anodic oxidation treatment by a conventional method, only a gold-colored colored film can be obtained. , called the gold coloring method).

In the electrolytic coloring method of the present invention, color development as in the present invention is not caused by simply adding secondary anodizing treatment by alternating current electrolysis to the ordinary electrolytic coloring method, but rather, the color development as in the present invention is not caused by the addition of the secondary anodizing treatment and the first anodizing treatment. In combination with gold coloring treatment by alternating current electrolysis in an electrolytic coloring bath containing tin salts and degradable sulfur compounds,
When the amount of tin and decomposable sulfur compounds adsorbed into the micropores of the modified anodic oxidation treatment increases,
The reddish ocher color of the present invention can be seen.

That is, in the electrolytic coloring method of the present invention, AC electrolysis is performed in a sulfuric acid bath as an intermediate treatment between the anodizing treatment and the electrolytic coloring treatment of the gold coloring method to form a double film structure, and the double layer of the anodic oxide film is film structure,
A reddish ocher colored film is formed by skillfully combining the stannous salt and an alternating current electrolytic coloring treatment in an electrolytic coloring bath containing the decomposable sulfur compound. .

Aspects of the Invention To explain the present invention in detail, first, an aluminum material is subjected to treatments such as degreasing, etching, neutralization, washing with water, and removal of smut according to a conventional method as required, and then approximately 100 to 300 g of aluminum material is processed according to a conventional method. Direct current electrolysis in a primary sulfuric acid bath containing sulfuric acid at a concentration of /,
A primary anodic oxide film having a thickness of approximately 9 to 13 μm is formed. For this primary anodizing treatment, it is sufficient to perform electrolytic treatment by using an aluminum material as an anode and applying a DC voltage between it and a suitable counter electrode according to a conventional method.
Electrolytic conditions such as applied voltage, current density, bath temperature, etc., as well as conventional methods are sufficient. Additionally, other organic acids and inorganic acids may be added to the sulfuric acid bath.

Next, the aluminum material that has undergone the primary anodizing treatment is subjected to a secondary anodizing treatment by alternating current electrolysis in a second sulfuric acid bath. 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
In the next electrolytic coloring process, the amount of tin and decomposable sulfur compounds adsorbed into the micropores of the anodizing treatment is increased, thereby achieving a reddish ocher color. It has the significance of
The dissociation reaction caused by AC electrolysis in this second sulfuric acid bath is estimated as follows.

2SO ₄ ^2- +17H ⁺ +14e→SH ^- +S+8H ₂ O Or, H ₂ SO ₄ +4H ₂ →H ₂ S+4H ₂ O H ₂ SO ₄ +H ₂ S→S+SO ₂ +2H ₂ O Due to the above reaction, sulfur and It is thought that a sulfur compound is included, which promotes the formation of metal sulfides in the next electrolytic coloring process, resulting in the formation of a reddish ocher colored film.

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. The bath temperature is 100-30°C, preferably 15-25°C, more preferably 18-23°C. At a high temperature of 30° C. or higher, peeling of the oxide film or a powder blowing phenomenon 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 electrolytic conditions, the current density is 0.5~
3A/ ^dm2 , preferably 1.0 to 2.5A/ ^dm2 , more preferably 1.5 to 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. Further, 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.

As mentioned above, aluminum materials that have undergone secondary anodization treatment by AC electrolysis in a secondary sulfuric acid bath,
Next, alternating current electrolysis is carried out in an electrolytic coloring bath containing at least one of a stannous salt and a decomposable sulfur compound to effect electrolytic coloring.

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 as stannous chloride), preferably considering the cost, the amount of the stannous component is 1.0 to
20g/(approximately 1.8 to 35g/as stannous sulfate)
It is.

“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, pyrosulfurous acid, 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 salts such as sodium, potassium, and ammonium, 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 as the amount of sulfur component in the molecule.
0.12-15g/degree (thioglycolic acid HSCH ₂
about 0.43 to 54 g/) as COOH.

At least one selected from the group of stannous salts and the group of "decomposable sulfur compounds" mentioned above is added to the electrolytic solution, and sulfuric acid is added as an electrolyte component to provide further conductivity. A stannous antioxidant may also be added.

In addition to the sulfuric acid mentioned above, inorganic acids such as sulfuric 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, Organic acids such as tartaric acid and citric acid, or their ammonium salts, amino salts, or imino salts can also be used in combination, and an aqueous solution of these is used as an electrolyte and the above-mentioned compounds are added thereto to prepare an electrolytic coloring bath. Furthermore, 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 about 5 g/
That's it (up to the saturation point).

Adding an antioxidant to prevent the oxidation of stannous to stannic is useful because tin salts are expensive and to keep the bath concentration 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 is, 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.

After the electrolytically colored anodic oxidation treatment as described above, a pore sealing treatment using boiling water, chemicals, pressurized steam, etc. is performed as necessary. Further, after performing this sealing treatment, or without performing the sealing treatment, the surface may be further protected by dip coating or electrolytic 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 of the Invention Coupled with the effect of the secondary anodizing treatment by alternating current electrolysis in the secondary sulfuric acid bath, the anodic oxide film of the aluminum material electrolytically colored according to the present invention loses its glossiness. A colored film having an ocher color tone with a reddish wood texture and excellent corrosion resistance and weather resistance can be obtained.

In addition, the decomposable sulfur compound contained in the electrolytic coloring bath has the effect of improving the spreading property, and together with the effect of the secondary anodic oxidation treatment by alternating current electrolysis in the second sulfuric acid bath, the coloring The progress rate is good, so electrolytic coloring can be carried out in a relatively short period of time, and ocher colored films can be uniformly formed even on shapes with complex shapes.

Therefore, the electrolytic coloring method of the present invention can be said to be extremely practical in terms of productivity, workability, and quality, as well as in terms of user needs for coloring intermediate between bronze and gold.

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

Example 1 Pressed aluminum material A-6063S which had been degreased, etched and smutted by conventional methods was heated to 18W/V.
% sulfuric acid aqueous solution to serve as an anode and an aluminum cathode provided as a counter electrode, a 15V DC current was applied at a current density of 1.0A/dm ² for 35 minutes.
A 9 micron anodized layer was formed on its surface. This was washed with water, carbon was used as the counter electrode, and sulfuric acid was used.
AC electrolysis was performed for 10 minutes at a current density of 2.0 A/dm ² in a 18 W/V% bath, and then immersed in an electrolytic solution at 18°C having the following composition (particularly the essential condition is that it contains a large amount of decomposable sulfur). When AC electrolysis was performed for 8 minutes at an applied voltage of 8 V, a dull, reddish ocher color with a woody texture was obtained.

Electrolyte composition: Stannous sulfate 8g / Sulfuric acid 40g / Sodium thiosulfate 2g / Formalin (37% aqueous solution) 25g / Comparative example 1 After pretreatment, extruded shape A-6063S was immersed in a 18W/V% sulfuric acid aqueous solution. A direct current was applied between the anode and the aluminum cathode provided as a counter electrode at a current density of 1.0 A/dm ² for 35 minutes to form an anodic oxide film of 9 microns on the surface. Wash this with water, use carbon as the counter electrode, and use 18W/V% sulfuric acid.
AC electrolysis was performed for 10 minutes at a current density of 2.0 A/dm ² in a bath of Although alternating current electrolysis was carried out for 8 minutes, only a pale gold color was obtained, which was completely different from the dull, reddish, woody ocher color, and such a color could not be obtained.

Electrolyte composition: Stannous sulfate 8g/ Sulfuric acid 40g/ Formalin (37% aqueous solution) 25g/

Claims (1)

[Claims] 1 Aluminum or its alloy is anodized by direct current electrolysis in a first sulfuric acid bath, then subjected to a second anodization treatment by alternating current electrolysis in a second sulfuric acid bath, and then treated with stannous salt. , sulfuric acid, and a substance that has sulfur atoms in its molecules and releases the contained sulfur by gradually decomposing in the liquid or decomposing by undergoing an oxidation-reduction reaction by alternating current current. 1. A method for electrolytically coloring aluminum or an aluminum alloy, the method comprising performing alternating current electrolysis in an aluminum alloy to form a reddish ocher colored film on the surface of the aluminum or aluminum alloy. 2. The method according to claim 1, in which the same sulfuric acid bath is used as the first sulfuric acid bath and the second sulfuric acid bath.