PURPOSE: To perform the beautiful and anticorrosive treatment of the surface of a nonferrous metal plate by forming a thin film comprising a resin produced by curing an acrylpolyol resin with hexamethylenediisocyanate on the surface of the nonferrous metal plate.

CONSTITUTION: The resin composition comprising (A) an acrylpolyol resin as a main 7 component and (B) hexamethylenediisocyanate as a curing agent in an A/B ratio of 2-5/0.5-2 is coated on the surface of a nonferrous metal plate (e.g. stainless steel, aluminum alloy) by an airless spraying method, by an air spray coating method, etc., in a dry coating film thickness of 20-50μm to form a thin coating film on the surface of the plate in a good adhesion state for the beautiful decoration and anticorrosion of the plate. The acrylpolyol resin (A) is produced by copolymerizing styrene, methyl methacrylate, butyl acrylate and 2-hydroxyethyl acrylate in amounts of 1-50 pts.wt., respectively, and subsequently diluting the produced copolymer with a solvent mixture (xylene:ethyleneglycol monoethylether acetate =7:3) to give a solid content of 50%.