METHOD FOR IMPARTATION OF BLUE COLOR TO ALUMINUM OR ALUMINUM ALLOY

摘要

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.