JPS58161796A - Method for coloring anodic oxide film of aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To easily form a finely and deeply colored film with superior corrosion and weather resistances, by electrolytically coloring Al or an Al alloy having a formed anodic oxide film in an electrolytic bath contg. nickel sulfate, ferrous sulfate and boric acid as essential components. CONSTITUTION:Al or an Al alloy provided with an anodic oxide film is electrolytically colored in an electrolytic bath contg. nickel sulfate, ferrous sulfate and boric acid as a pH buffer as essential components. By the electrolysis Ni ions and Fe ions are reduced and deposited in the pores of the anodic oxide film to color the film black. Treatment for sealing pores or coating is then carried out by a conventional method to obtain a desired colored film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for imparting a desired color, particularly a deep color, to an anodized film produced by anodizing aluminum or an aluminum alloy (hereinafter abbreviated as aluminum material).

Conventional electrolytic coloring methods for aluminum materials include a method in which an aluminum material on which an anodic oxide film is formed by secondary electrolysis is subjected to secondary electrolytic coloring using alternating current in an electrolytic bath containing dissolved metal salts; A method is known in which an aluminum material anodized by primary electrolysis in a dissolved electrolytic bath is used as a cathode, and secondary electrolytic coloring is performed by direct current. However, these methods cause uneven coloring, difficulty in controlling the electrolytic bath, and peeling of the colored film, making it difficult to obtain a dark and beautiful colored film. Typical examples of secondary electrolytic baths for black coloring include nickel sulfate as a metal salt for coloring, ammonium llillate as a PHIII effect agent, boric acid, phenolsulfonic acid as a soluble effect agent, and antioxidant effect agent. A solution is known in which hydrazine sulfate is added as a coating agent, magnesium chloride is used as a film defect (spalling) preventive agent, and a Sendai type additive is added thereto. Although this electrolytic bath is characterized by good stability, it has the disadvantage that it is difficult to obtain a deep color, and this tendency is particularly strong when AC electrolysis is performed. In order to solve this problem, studies are being carried out such as adding another metal salt or replacing it with another metal salt. However, when using an electrolytic bath in which stannous sulfate is added to the nickel sulfate as a metal salt, a dark colored film can be obtained due to the eutectoid of tin and nickel. Due to the low solubility, the bath concentration fluctuates widely, and tin is oxidized from divalent to tetravalent during electrolysis, resulting in unstable colored tone and F"I of the electrolytic bath.
Due to the low t (2 or less), some of the anodic oxide film is eluted in the electrolytic bath and the color tone tends to fluctuate.
When using a plurality of metal salts as components of an electrolytic bath for coloring, there are various problems to be solved regarding the combination thereof.

The present invention has been achieved by discovering a coloring method that eliminates the drawbacks of the conventional electrolytic coloring methods described above by specifying the components of the coloring electrolytic bath. The gist of this method is to electrolytically color an aluminum material in an electrolytic bath containing nickel sulfate, 1/1A of 1ilt acid, and boric acid as essential components.

To explain the present invention in more detail below, the aluminum material on which the anodic oxide film of the present invention has been formed is prepared by subjecting the aluminum material to pre-treatments such as degreasing and etching in accordance with conventional methods, and then applying a solution of various inorganic acids, organic acids, etc. immersed in a primary electrolytic bath consisting of, for example, direct current or other voltage waveform current at a temperature of 25° C. at a voltage of 15 to 25 V and a current density of 0.
It is obtained by conducting for 10 to 60 minutes at 5 to 2 A/d rrr. Specific examples of the primary electrolytic bath used here include solutions of sulfuric acid, phosphoric acid, oxalic acid, etc. However, considering film-forming properties, electrolytic bath management, economic efficiency, etc., it is preferable to use sulfuric acid. is most preferred.

Although the concentration of the electrolytic bath is not particularly limited, for example, in the case of sulfuric acid, it is effective even at 5%, and the effect does not decrease even at a high concentration of 25% or more.

However, considering ease of operation and economical processing, 10
A concentration of ~20% is suitable.

In the present invention, an aluminum material having an anodic oxide film formed thereon as described above is colored by secondary coloring electrolysis.

In the present invention, the secondary coloring electrolytic bath includes, as a coloring metal salt,
It contains nickel sulfate, ferrous sulfate, and boric acid as a pH buffering agent as essential components. Since iron ions co-deposit with nickel ions, the electrolytic bath can be colored darker than an electrolytic bath containing only nickel. When preparing the secondary colored electrolytic bath, in addition to the essential components listed above, if necessary, for example, phenol sulfonic acid, cresol sulfone m
Other additives can be added such as ammonium sulfate (Pl (buffer), magnesium chloride (anti-spalling agent), which brings the bath PH from 3 to 4.5, preferably from 3.5 to The bath concentration of the essential components nickel sulfate, ferrous sulfate, or boric acid is adjusted depending on the desired coloring density, but typical bath compositions include nickel sulfate 100-150%. (+/text, sulfuric acid 1st ridge 1
0 to 60 g 7·', and boric acid 20 to 50 g/stand.

For secondary coloring electrolysis, in addition to alternating current and direct current, an alternating current and direct current superimposed power source, repeated conduction of alternating current and direct current, and a pulse power source are used as a power source. The voltage varies depending on the bath temperature, distance between electrodes, sample area, etc., but 15 to 25 V is appropriate.

In addition, since the deposition potential of the ridge ions is relatively base, they are more difficult to deposit than other metals such as copper ions, tin ions, cobalt ions, lead ions, manganese ions, etc. )
I! Since it has low wear and high solubility in water, it is possible to prepare a high-concentration colored electrolyte bath, and the color variation of the colored film is small.

When secondary electrolysis is performed in this way, the nickel ions and iron ions in the electrolytic bath are reduced and deposited in the pores of the anodic oxide film, which is colored deep black. The desired colored skin can be obtained by treatment or painting.

As described in detail above, the present invention uses an aluminum material on which an anodized film has been formed in a colored electrolytic bath containing as essential components a metal salt consisting of a combination of nickel sulfate and ferrous sulfate, and boric acid. This method is characterized by secondary electrolysis, which allows the aluminum material to be colored evenly and in a deep color. Further, even when alternating current is used in the W color electrolytic process, metal deposition is not slowed down so much, and film defects such as spalling are less likely to occur even when direct current is used. Furthermore, the colored electrolytic bath itself is stable and has the advantage that work management is easy.

According to the present invention, the colored aluminum material has excellent corrosion resistance and weather resistance, and has a deep beautiful color tone.
It also has a decorative effect and can be applied to a wide range of fields including building materials.

EXAMPLES The present invention will be explained in more detail by Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 An extruded AA6063 aluminum mold material containing 0.15% iron was degreased and etched according to a conventional method, and then immersed in a primary electrolyte consisting of a 15% sulfuric acid aqueous solution, and a direct current was applied at a temperature of 20°C. Conductivity was carried out for 40 minutes at a density of IA/drrf and washed with water to form an anodic oxide film with a thickness of 6 μm. Next, nickel sulfate 609/vert, boric acid 40
Five types of secondary coloring electrolytic baths containing ferrous sulfate and ferrous sulfate at concentrations shown in Table 1 below were prepared, and the extruded aluminum mold material on which the anodic oxide film was formed was immersed in the baths. , temperature 25℃, AC current voltage 14V, current density fl
[o, Electrolyzed for 3 minutes at 7A/d rrr. The color density of the obtained colored film was measured using a color difference meter (Nippon Denshoku Kogyo ND10).
The L value was measured for Type 1) and the results shown in Table 1 were obtained.

As is clear from the above results, by using a colored electrolytic bath in which nickel sulfate and ferrous sulfate coexist, L
It can be seen that a very dark colored film with a value of 18 to 24 can be obtained.

Example 2 The same aluminum extrusion material as in Example 1 was used in Example 1.
An anodic oxide film having a thickness of 6 μm was formed by processing under the same conditions as above. Next, a secondary coloring electrolytic bath was prepared containing nickel sulfate 60 (+, '), boric acid 40Q/C, and sulfuric acid No. The extruded material was immersed, and this was used as an anode, and the nickel plate was used as a counter electrode at a temperature of 1 [25°C,
AC tR current voltage 14V, 1115It density fIo, 7
A/(l rr [-1 minute 111 colors were electrolyzed, and in the same electrolytic bath, the aluminum extruded material was used as a cathode, and a DC current was applied for 1 minute at a voltage of 16 V, a current density of 0.8 A, and /dr+?) for 1 minute. , L 16 was 18, and a uniformly colored, defect-free black colored film was obtained.

On the other hand, as a comparative example, an aluminum extruded material treated under the same conditions as in Example 2 to form an anodized film was immersed in the same colored electrolytic bath as in Example 2, except that it did not contain ferrous sulfate. When colored electrolytically treated under the same conditions as in Example 2, the obtained colored film had an L value of 21.3 and was lighter in color than in Example 2, with some spalling occurring.

Agent: Patent Attorney Tsutomu Adachi

Claims (1)

[Scope of Claims] 1. An aluminum or aluminum alloy characterized by electrolytically coloring aluminum or an aluminum alloy on which an anodic oxide film has been formed in an electrolytic bath containing nickel sulfate, a fall first ridge, and boric acid as essential components. Coloring method for aluminum alloy anodic oxide film. 2. The aluminum or aluminum alloy fi polar oxide film according to claim 1, wherein the electrolytic coloring is performed using an AC power source, a DC power source, a 4 AC/DC Φ tatami power source, a pulse power source, or repeated use of an AC power source and a DC power source. How to color.