Abstract: Anodized films having an aesthetic value are formed over the surface of aluminum or aluminum alloy substrates by anodizing the substrate in an electrolyte solution containing 50-60% of sulfuric acid and oxalic acid or nickel sulfate, at a bath temperature of 18.degree. to 30.degree. C. and a current density of 1 to 10 A/dm.sup.2.The oxide film formed by this method has a porcelain-like texture or feel or the appearance of a meshwork thereof or a grainy texture resembling wood, leather or sand, depending upon the nature of the base or substrate metal and the anodizing conditions employed.

Abstract: Anodizing of aluminum or aluminum alloys at an exceptionally high film forming rate is conducted by the employment of a current density greater than 1.5 A/dm.sup.2 and a concentration of sulfuric acid of from 20% to 30% by weight in an electrolyte solution bath, and by the use of a racking device and cooling device which is designed for said severe conditions of current density and sulfuric acid concentration. A careful selection and regulation of the anodizing temperature enables the option of forming a soft or hard oxide film of greater thickness than achieved heretofore. Bath temperatures of around 30.degree. C. permit the formation of a soft oxide film, while bath temperatures of around 5.degree. C. permit the formation of a hard oxide film.