ANTICORROSIVE BLACK COATING ON ZINC ALLOY AND METHOD FOR MAKING SAME

摘要

The invention concerns a method for depositing an anticorrosive black coating on a zinc alloy which consists in treating the zinc alloy in a first step with an aqueous acid solution of Cr3+ containing one or several complexing agents and in treating the resulting passivated zinc alloy in a second step with an aqueous suspension containing organic polymers and anticorrosive metal oxides and black pigments. The invention also concerns a black anticorrosive coating with two layers on a zinc alloy, the first layer of the anticorrosive coating having a weight (in Cr) of 1 to 4 mg/dm<2>.