Metal oxide film

Patent Granted PROBLEM TO BE SOLVED: To provide a method of forming a metal oxide film suitable for the protection of a metal containing aluminum as a main component. ; SOLUTION: In the method of manufacturing a metal member, a metal material containing aluminum as a main component is anodized in an anodization solution having a pH of 4 to 10 and containing a nonaqueous solvent having a dielectric constant smaller than that of water and capable of dissolving water, thereby forming a nonporous amorphous aluminum oxide passivation film on a surface of the metal member.