Yoshida Kogyo K.k.

Norio Nakada

Hatsuo Hirono

Hideo Fukui

Seishiro Ito

A fast and brightly colored oxide film of aluminum which excels in durability and allows no separation of pigment is produced by using an aqueous dispersion of an organic pigment or carbon black finely divided to a size in the range between 3 and 150 nm, forming on a surface of an aluminum member an anodic oxide film containing pores larger in diameter than the ordinary pores, and causing the organic pigment or carbon black to migrate and deposit in the pores of the oxide film by means of electrophoresis. The formation of the anodic oxide film containing the pores larger in diameter than the ordinary pores is accomplished in the first method by subjecting the aluminum member to anodic oxidation at a high voltage in an aqueous solution of acid. In the second method, the anodic oxide film is subjected either to a treatment of immersion in an aqueous solution of at least one acid selected from among phosphoric acid, sulfuric acid, oxalic acid, and sulfamic acid or to a combination treatment of immersion and AC electrolysis repeated in a prescribed number of cycles in the solution, to enlarge the pores in the anodic oxide film.

Method for production of colored article of aluminum or aluminum alloy

Durable and clear blue color of freely controlled density can be expeditiously and efficiently impated to an anodic oxide film of aluminum by a method which comprises forming the anodic oxide film on the aluminum or aluminum alloy, then subjecting the aluminum or aluminum alloy to AC electrolysis in a bath containing an inorganic ferrous salt as a main component thereof thereby inducing deposition of iron in the pores of the oxide film, and subsequently placing the aluminum or aluminum alloy as an anode in a bath containing hexacyano iron (II) acid salt as a main component thereof and subjecting the same to DC electrolysis therein. In the alternative method, the pore-widening treatment is added next to said step of anodic oxidation. The pore-widening treatment is effected by immersing the aluminum or aluminum alloy in sulfuric acid or phosphoric acid or electrolyzing the same in phosphoric acid or a mixed solution of phosphoric acid and sulfuric acid.

Method for impartation of blue color to aluminum or aluminum alloy

An aluminum or aluminum alloy material is subjected to anodic oxidation, then to a treatment of electrophoresis in a bath containing a hexacyanoferrate (II) or hexacyanoferrate (III), and subsequently to a treatment of immersion in a bath containing at least one metal salt selected from the group consisting of salts of Fe, Ni, Co, Cu, Zn, Cd, Ba, Tl, and Mg and at least one electrolyte selected from the group consisting of sodium sulfate, potassium sulfate, sodium chloride, and potassium chloride. Consequently, a coloring compound formed by the reaction of the aforementioned hexacyanoferrate (II) or hexacyanoferrate (III) with the aforementioned metal salt is deposited in the receding parts of micropores of an anodic oxide coating, with the result that the aluminum or aluminum alloy material is endowed with a durable color.

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Toyama, Japan

Norio Nakada