Method for electrically coloring aluminum material and gray-colored aluminum material obtained thereby

Abstract

Disclosed are a method for electrolytically coloring an aluminum material which is capable of coloring an anodic oxide film in a gray color and a gray-colored aluminum material obtained thereby. In a method for electrolytically coloring an aluminum material having the anodic oxide film formed on the surface thereof in an electrolytic coloring solution containing an inorganic metal salt, a strongly acidic electrolytic coloring solution containing sulfuric acid, stannous sulfate, nickel sulfate, and ammonium sulfate and having a pH of not more than 2.5 is used as the electrolytic coloring solution. Preferably the electrolytic coloring solution contains sulfuric acid at a concentration in the range of 3 to 30 g/liter, stannous sulfate at a concentration in the range of 0.1 to 3.0 g/liter, nickel sulfate at a concentration in the range of 10 to 100 g/liter, and ammonium sulfate at a concentration in the range of 20 to 100 g/liter. By this method, a gray-colored aluminum material possessed of an anodic oxide film colored in an achromatic or substantially achromatic gray color is obtained.

Dependencies are inferred from the claim text.