Patent ID: 8658275

Claim:
A surface-treated metal plate comprised of a metal sheet on one surface or both surfaces of which two or more coating layers are provided, the surface-treated metal plate is characterized in that the two or more coating layers are formed by water-based dispersion coatings or emulsion coatings, a diffusion layer is formed at an interface part between a first coating layer as a top layer and a second coating layer as a bottom layer, wherein one of the first or the second layer contains rust preventing pigments and the other does not contain rust preventing pigments, wherein the concentration of rust preventing pigments in the diffusion layer changes from 2 mass % to 98 mass % with respect to concentration of the rust preventing pigments in the one of the first and the second layer in the film thickness direction found by analysis of the rust preventing pigments in the coating depth direction by high frequency GDS, and in that t/T is 0.2≦t/T≦0.8 where the film thickness of said diffusion layer is “t” and the total film thickness of said diffusion layer, said first coating layer, and said second coating layer is “T”.