Protective conversion coating on mixed-metal substrates and methods thereof

摘要

Mixed-metal automotive vehicle bodies-in-white comprising ferrous metal surfaces, zinc surfaces, aluminum alloy surfaces, and magnesium alloy surfaces are cleaned and immersed in an aqueous bath comprising an adhesion promoter and an aqueous electrocoat bath (the adhesion promoter may be in the electrocoat bath. The adhesion promoter, which may be a cerium salt, is selected to react with each metal in the body surfaces to form an oxide layer that provides corrosion resistance for the surface and adherence for the deposited polymeric paint coating. The body is cathodic in the electrocoat deposition.

主权项

1. A method of forming a protective conversion coating on a mixed-metal substrate, the method comprising:
contacting a cerium salt and an oxidizing agent, sufficient to form a protective conversion coating solution; providing a mixed-metal substrate having a plurality of joined metal surfaces, at least one of the surfaces comprising magnesium, and at least one of the surfaces comprising ferrous metal, zinc, or aluminum; and depositing the protective conversion coating solution on each metal surface of the mixed-metal substrate to form a protective metal coating conversion solution layer, and wherein any metal present is selected from the group consisting of cerium and one or more metals of the mixed-metal substrate.