METHOD FOR ELECTROLYTICALLY COLORING ANODIC OXIDE FILM ON ALUMINUM OR ALUMINUM ALLOY

摘要

PURPOSE:To mass-produce coating films having a fine color tone and superior durability in a short time at a low cost by successively impressing DC voltage and AC voltage on each anodic oxide film on Al in an electrolytic coloring bath contg. specified amts. of copper pyrophosphate, nickel sulfate and sulfuric acid. CONSTITUTION:When an anodic oxide film on Al or Al alloy is electrolytically colored, a mixed soln. contg. 20-50g/l copper pyrophosphate, 75-150g/l nickel sulfate and 20-50g/l sulfuric acid is used as an electrolytic coloring bath. DC voltage is impressed on the film as the anode in the bath and then AC voltage is impressed on the film. A uniform colored coating film similar to clear japan and having superior durability is efficiently formed without adding an expensive component such as silver.