JPH04246195A - Method for coloring aluminum anodic oxide film - Google Patents

Abstract

PURPOSE:To easily color an Al anodic oxide film in various color tones by electrolyzing the film in an electrolytic bath contg. Ni salts, Fe salts, etc., and then AC-electrolyzing the film in an aq. soln. contg. a thiocyanate. CONSTITUTION:An Al anodic oxide film 1 is formed on the surface of an Al base material 4 by anodization through a barrier layer 5. The film is again anodized to form a pore 2a of bottle-shaped profile. The film 1 is then electrolyzed in an electrolytic bath contg. one or plural kinds of salts among the Ni, Fe, Cd, Cr, Co, Mn and Cu salts, and a deposit resulting from the metal salts in the bath is formed in the pore 2a. The film 1 is Ac-electrolyzed in an aq. soln. contg. a thiocyanate to convert the deposit into the thiocyanide 3a. Consequently, various color tones are easily controlled by the thiocyanide, and the film 1 is colored.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coloring an anodic oxide film of aluminum or its alloy, and it relates to a method that can easily control and obtain a variety of color tones based on thiocyanide.

0002

BACKGROUND OF THE INVENTION With the recent diversification of consumer lifestyles and demand preferences, products made of aluminum or its alloys are required to be colored in various colors. This coloring is generally performed by electrolytically treating an anodic oxide film of aluminum or its alloy (hereinafter referred to as aluminum anodic oxide film) to generate colored precipitates in the pores on the surface of the film.
For example, a method is known in which a simple metal is precipitated and colored to a color unique to the metal (Japanese Patent Application Laid-open Nos. 51-99640, 53-22834, 54-85137, etc.). And the times demand an even greater variety of color tones.

0003

OBJECTS OF THE INVENTION It is an object of the present invention to provide a method for coloring an aluminum anodic oxide film that can easily control and obtain a variety of color tones based on thiocyanide.

0004

[Means for achieving the object] The method for coloring an aluminum anodic oxide film of the present invention is to color an aluminum anodic oxide film by treating the aluminum anodic oxide film with Ni salt, Fe salt, Cd salt, Cr salt, Co salt, Mn salt,
Electrolytic treatment is performed in an electrolytic bath containing one or more Cu salts to form a precipitate based on the metal salt in the electrolytic bath in the pores on the surface of the film, and then an aqueous solution containing thiocyanate. The method is characterized in that the precipitate is converted into thiocyanide by alternating current electrolysis.

Further, in the present invention, it is preferable to use an aluminum anodic oxide film in which the pores on the surface of the film are shaped like a bottle in longitudinal section by re-anodizing.

[0006] A normal anodic oxidation method is used to form the aluminum anodic oxide film. That is, for example, inorganic acids such as sulfuric acid, phosphoric acid, chromic acid, or organic acids such as oxalic acid, sulfosalicylic acid, malonic acid, or sodium hydroxide,
It is formed by electrolysis using direct current, alternating current, pulse, PR waves, or AC/DC superposition method in an electrolytic bath of an alkaline aqueous solution such as trisodium phosphate.

[0007] Re-anodizing treatment uses phosphoric acid, pyrophosphoric acid,
This is carried out by electrolyzing in an electrolytic bath of sulfuric acid or a mixed acid thereof in the same manner as the anodic oxidation treatment described above.

[0008] Electrolytic treatment in an electrolytic bath containing one or more salts selected from Ni salt, Fe salt, Cd salt, Cr salt, Co salt, Mn salt, and Cu salt is carried out using a counter electrode in the bath. For example, carbon is used and an alternating current or direct current voltage is applied. Additionally, additives such as boric acid and sulfuric acid may be added to the bath.

Electrolytic treatment in an aqueous solution containing thiocyanate is carried out by applying alternating current voltage or alternating forward and reverse pulses. As the thiocyanate, for example, ammonium thiocyanate is used.

After the alternating current electrolytic treatment, a usual sealing treatment is performed.

[0011]

[Operation] The aluminum anodic oxide film obtained by the usual anodic oxidation method is porous as shown in FIG. 1, which is a schematic cross-sectional view. In the figure, 1 is an aluminum anodized film, 2 is a hole, 4 is a base material of aluminum or its alloy, and 5 is a barrier layer.

When the re-anodizing treatment is performed, the diameter L (FIG. 1) of the pores 2 of the coating 1 is enlarged, and the pores 2a having a bottle-shaped longitudinal section as shown in FIG. 2 are obtained.

[0013] Then, the previous electrolytic treatment, that is, Ni salt, Fe salt,
By electrolytic treatment in an electrolytic bath containing one or more salts of Cd salt, Cr salt, Co salt, Mn salt, and Cu salt,
As shown in the figure, a precipitate 3 based on the metal salt contained in the bath is formed in the hole 2a. This precipitate 3 is obtained in the following states: (1) an elemental metal, (2) a mixture of an elemental metal and a metal oxide or hydrate, or (3) a metal oxide or hydrate. . The amount of precipitation can be controlled relatively easily by adjusting the voltage and time during electrolytic treatment.

Then, by a subsequent electrolytic treatment, that is, an AC electrolytic treatment in an aqueous solution containing thiocyanate, the precipitate 3 is changed into a thiocyanide 3a, as shown in FIG. In this electrolytic treatment, when the voltage is sufficiently high and the electrolysis time is sufficiently long, all of the precipitates 3 become thiocyanide, but when this is not the case, only a part of the precipitates 3 becomes thiocyanide. That is, the rate of conversion to thiocyanide can be easily controlled by adjusting the voltage and time during electrolytic treatment.

By the way, the color tone of each metal thiocyanide is as follows. CuSCN (white), Fe (SCN)2 (
(dark red), Fe (SCN)3 (dark red), Cd (SCN
) 2 (white), Cr (SCN) 3 (green), Co (SCN)
2 (red or green), Ni (SCN) 2 (yellow or green), Mn
(SCN)2 (yellow or green). Therefore, in the later electrolytic treatment, if all of the precipitate 3 becomes thiocyanide,
The color tone of the film will be the above-mentioned color tone, but if only a part of the precipitate 3 becomes thiocyanide, the color tone will be a mixture of the color tone of the precipitate 3 and the color tone of the thiocyanide. These color tones vary from light to dark depending on the amount of precipitate 3 obtained in the previous electrolytic treatment.

That is, according to the present invention, in addition to the change in color tone from light to dark based on the amount of precipitate 3, the color tone of precipitate 3 and the color tone of thiocyanide are mixed based on the rate of conversion to thiocyanide. The resulting color tones are very diverse, and the amount of precipitate 3 and the rate of conversion to thiocyanide can be easily controlled, making it possible to obtain a wide variety of colors. A desired color tone can be easily obtained from among various color tones.

[0017] In the above, the case where the re-anodized film shown in Fig. 2 is used is explained, but similarly when the anodized film shown in Fig. 1 is used, the color tones obtained are very diverse. Moreover, the desired color tone can be easily obtained from among a variety of color tones. However, when a re-anodized film is used, the reaction efficiency is good because the contact area between the precipitate 3 in the pores and the electrolyte is large, so the conversion to thiocyanide progresses smoothly and the resulting product is The resulting color tone is clearer and darker.

[0018]

Effects of the Invention As described above, according to the present invention, in addition to a change in color from light to dark, a change in color from a mixed color of precipitates and thiocyanide to a color of thiocyanide can be realized. It is possible to obtain a wide variety of color tones. Moreover, since the amount of precipitates and the rate of conversion to thiocyanide can be easily controlled, a desired color tone can be easily obtained from among a variety of color tones.

Furthermore, by using an aluminum anodic oxide film in which the pores on the surface of the film have become bottle-shaped in longitudinal section by re-anodizing, a clearer and darker color tone can be obtained.

[0020]

[Example] Aluminum extruded shape (JIS designation “A60”)
63S-T5'') was anodized in a sulfuric acid bath to form a 9μ
An anodic oxide film (hereinafter referred to as the first film) having a thickness of m was obtained. Further, the first film was re-anodized by applying a DC voltage of 16 V for 10 minutes in a 10% by weight phosphoric acid bath at 25°C, so that the pores on the film surface became bottle-shaped in vertical section. A film (hereinafter referred to as a second film) was also obtained. For each of the first and second films, a first electrolytic treatment was performed under various conditions shown in Table 1, and a subsequent electrolytic treatment was performed under various conditions shown in Table 2. The table also shows the color tones obtained. Further, A to H in Table 1 indicate the obtained first coatings, and Table 2 indicates that the first coatings A to H in Table 1 were used.

[0021]

[Table 1]

[0022]

[Table 2]

As shown in Table 2, a wide variety of color shades based on thiocyanide were obtained. Furthermore, when the second film was used, the color tone was clearer and darker.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an aluminum anodic oxide film.

FIG. 2 is a schematic cross-sectional view showing an aluminum anodized film that has been re-anodized.

FIG. 3 is a schematic cross-sectional view showing the aluminum anodic oxide film after the previous electrolytic treatment.

FIG. 4 is a schematic cross-sectional view showing an aluminum anodic oxide film after subsequent electrolytic treatment.

[Explanation of symbols]

1 Aluminum anodic oxide film 2, 2a hole 3 Precipitate 3a Thiocyanide 4 Base material

Claims (2)

[Claims] Claim 1: Aluminum anodic oxide film is coated with Ni salt, F
Electrolytic treatment is performed in an electrolytic bath containing one or more salts of e salt, Cd salt, Cr salt, Co salt, Mn salt, and Cu salt to form metal salts in the electrolytic bath in the pores on the surface of the film. 1. A method for coloring an aluminum anodic oxide film, the method comprising: forming a precipitate based on thiocyanate, and then converting the precipitate into a thiocyanide by alternating current electrolysis in an aqueous solution containing thiocyanate. 2. The method for coloring an aluminum anodic oxide film according to claim 1, wherein the aluminum anodic oxide film is one in which the pores on the surface of the film are bottle-shaped in longitudinal section by re-anodizing treatment.