Patent ID: 8057858

Claim:
A process for the preparation of a corrosion-resistant, colored oxide layer on aluminum or an aluminum alloy comprising the steps of applying a polysilazane solution to a dry oxide layer colored with a water-soluble, anionic colorant to form a coating and curing the coating at a temperature in the range from 40 to 150Â° C., wherein the polysilazane solution comprises a solvent, a catalyst and a polysilazane or a mixture of polysilazanes of the formula 1 â€”(SiRâ€²Râ€³â€”NRâ€²â€³) n (1) where Râ€², Râ€³, Râ€²â€³ are identical or different and independently of one another are hydrogen or an optionally substituted alkyl, aryl, vinyl or (trialkoxysilyl)alkyl radical, where n is an integer and n is calculated such that the polysilazane or mixture of polysilazanes has a number average molecular weight of 150 to 150 000 g/mol, wherein the oxide layer has a thickness in the range from 5 to 30 Î¼m before the curing step, wherein the coating has a layer thickness of 1 to 10 Î¼m after the curing step.