Patent ID: 7097756

Claim:
A process for obtaining gold-colored aluminum oxide layers which comprises the following steps: a) pretreatment of aluminum or aluminum alloys; b) anodic oxidation of the aluminum or aluminum alloys (anodization); c) coloring of the oxidized surface of the aluminum or aluminum alloys by an electrolytic process in an electrolyte comprising an alkanesulfonic acid and an alkanesulfonate of silver; d) subsequent treatment of the gold-colored workpiece obtained after a), b) and c); e) if desired, recovery of the alkanesulfonic acid employed and/or its salts, it being possible for step e) to follow any step in which an alkanesulfonic acid is employed, in particular step b) and/or c) or to be carried out in parallel with these steps, wherein the coloring in step c) is carried out at a concentration of the alkanesulfonate of silver of from 2 to 50 g/l and a product of current density and voltage of from 0.5 to 10 AV/dm 2 over a period of from 0.05 to 4 minutes.