McNenny, Farrington, Pearne & Gordon
Method of forming colored oxide film on aluminum or aluminum alloy
 A method of forming a colored oxide film on the surface of an aluminum material is disclosed in which the aluminum material is subjected to an electrolytic treatment in an aqueous solution containing sulfuric acid to form an aluminum oxide film containing aluminous oxides and having lattice defects; sulfuric ions in the solution are caused to enter into the lattice defects of the oxide film; some or all of the sulfuric ions are reduced to form sulfur and sulfides; and the colored oxide film is formed using the sulfur and sulfides as coloring sources. 
Riken Light Metal Industries Company, Ltd.
C
C25D
inventional
Kenji Toshiro Yasushi Toshihiro
Wada Takahashi Suzuki Nagano