JPS6233318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic coloring method for aluminum or aluminum alloy (hereinafter referred to as aluminum) that has been subjected to anodizing treatment, and more specifically, the present invention relates to a method for electrolytically coloring aluminum or aluminum alloy (hereinafter referred to as aluminum) that has been subjected to anodizing treatment, and more specifically, it uses nickel sulfate and stannous sulfate as the coloring bath. This invention relates to a method for electrolytically coloring aluminum using a weakly acidic electrolyte as a component.

Conventionally, to color aluminum, a method is generally used in which the aluminum has been anodized to form an oxide film using a conventional method, and then an alternating current is applied in a coloring bath containing a metal salt to form the desired colored film. I came.

Acidic coloring baths are common as such coloring baths, but while they have the advantage of providing relatively good throwing power, they have high acidity (in other words, PH
It is known that due to the fact that the dye is not washed with water immediately after coloring, the color may come off, and bath management is also complicated.

On the other hand, an electrolytic coloring method for aluminum using a neutral or alkaline coloring bath has been proposed in Japanese Patent Application Laid-Open No. 49-58544, but such a neutral or alkaline coloring bath causes almost no color loss even without washing with water. However, it is known that the aging rate of the bath is extremely fast, making it difficult to manage the bath.

In addition, conventional acidic, neutral and weakly alkaline
Coloring baths in the PH range mainly produce bronze to black tones, and the problem of difficulty in obtaining other tones remains unsolved.

The present invention aims to solve the above-mentioned drawbacks of conventional coloring baths.More specifically, the present invention uses nickel sulfate and stannous sulfate as main coloring components, and adjusts and maintains the electrolytic coloring bath to be slightly acidic. An electrolytic coloring method for aluminum that prevents color fading and aging of coloring components, improves throwing power, and produces an excellent colored film that adds gray tones to the conventional bronze to black tones. The main purpose is to provide.

Therefore, in the electrolytic coloring method of aluminum of the present invention, anodized aluminum is subjected to alternating current in a weakly acidic electrolyte containing nickel sulfate and stannous sulfate as main coloring components, thereby creating a color tone unique to added metal salts. It is characterized by obtaining.

The pH range of the weakly acidic electrolyte may vary depending on the desired color tone and other coloring processing conditions. For example, when obtaining a gray tone, the pH range is 5 to
A range of 7 (excluding PH7) is desirable.

On the other hand, the concentrations of nickel sulfate and stannous sulfate in the weakly acidic electrolyte can also vary depending on the desired color tone and other coloring processing conditions, similar to the pH above, but generally each is 5 to 30 g/ and a range of 3 to 10 g/ is desirable. In particular, if more than 10 g of stannous sulfate is used, a large amount will precipitate in the coloring bath, which is undesirable.

Moreover, the above electrolyte solution further contains aluminum sulfate,
Appropriate amounts of boric acid and tartaric acid can be contained as necessary. Furthermore, it is possible to adjust the electrolytic solution as necessary, and when raising the pH (that is, bringing it closer to the neutral side), this is done by adding aqueous ammonia.

Other electrolytic coloring conditions, such as AC power supply voltage,
The frequency, current density, current application time, coloring bath temperature, etc. are appropriately selected from the ranges used in ordinary electrolytic coloring methods for aluminum. For example, it is preferable to select the voltage from the range of 13 to 17 V from the viewpoint of color tone and prevention of spalling.
Although the current application time can vary depending on the desired color tone and other coloring conditions, 1 to 10 minutes is usually appropriate. It is convenient to use a normal AC power supply as is, so the frequency is 50Hz or 50Hz.
It is 60Hz. Further, as a counter electrode, carbon, tin, nickel plate, etc. are used as in the conventional electrolytic coloring method.

According to the electrolytic coloring method of the present invention, in addition to the conventional bronze to black color tones, it has become possible to color gray colors, which have not been easily obtainable up to now.

Furthermore, the weakly acidic coloring bath used in the method of the present invention has superior corrosion resistance and throwing power compared to conventional acidic coloring baths, and has superior aging resistance than neutral and weakly alkaline coloring baths. found.

Next, examples of the present invention will be shown.

Example 1 After pre-treating an aluminum plate according to a conventional method,
Direct current electrolysis was carried out in a 150 g sulfuric acid bath to form a 14 μm anodic oxide film.

Next, alternating current electrolysis was carried out at 15 V for 5 minutes in an electrolytic coloring bath with the following composition and pH using carbon as a counter electrode, and a uniform bronze colored aluminum was obtained.

Bath composition: 6 g of stannous sulfate / 15 g of nickel sulfate / 20 g of tartaric acid / 20 g of ammonium sulfate / 20 g of boric acid / Bath PH: 5.5 Example 2 An aluminum plate was pretreated and anodized in the same manner as in Example 1, and anodized to 14 μm. A film was formed.

Next, alternating current electrolysis was carried out at 17 V for 10 minutes in the electrolytic coloring bath used in Example 1, using carbon as a counter electrode, and a uniform black colored aluminum was obtained.

Example 3 An aluminum plate on which a 20 μm anodic oxide film was formed in the same manner as in Examples 1 and 2 was subjected to alternating current electrolysis at 15 V for 2 minutes in the electrolytic coloring bath used in Example 2, and a uniform gray colored aluminum was obtained. It was done.

When the electrolytic coloring bath used in the above examples was analyzed, it was found that substantially no aging occurred. Furthermore, after the completion of the electrolytic coloring treatment, each colored aluminum was left as it was without being immediately washed with water, but almost no color fading was observed in any of the examples.

Claims (1)

[Scope of Claims] 1. PH containing nickel sulfate and stannous sulfate as main coloring components on anodized aluminum
A method for electrolytically coloring aluminum, which is characterized by applying alternating current in a weakly acidic electrolytic solution of 5-7 (not including pH 7) to obtain a color tone unique to an added metal salt. 2. In the electrolytic coloring method according to claim 1, the concentrations of nickel sulfate and stannous sulfate in the weakly acidic electrolyte are each 5-30 g/
, and electrolytic coloring of aluminum in the range of 3-10 g/. 3. The electrolytic coloring method for aluminum according to claim 1 or 2, wherein the weakly acidic electrolyte further contains ammonium sulfate, boric acid, and tartaric acid. 4. The electrolytic coloring method for aluminum according to any one of claims 1 to 3, wherein the weakly acidic electrolytic solution further contains ammonia water, and the pH is adjusted by the ammonia water.