SURFACE TREATED STEEL SHEET HAVING SUPERIOR RESISTANCE TO STRIPPING OF PAINT FILM

摘要

PURPOSE:To improve the resistance of a surface treated steel sheet to the stripping of a paint film by covering the surface of a Zn alloy plated steel sheet having an Fe-rich upper layer on a Zn-rich lower layer with an amorphous compound contg. Ca or Mo as the principal component. CONSTITUTION:A lower Zn alloy layer contg. >=50wt% Zn and an upper Zn alloy layer contg. >=50wt% Fe are formed on the surface of a steel sheet by electroplating or other plating method. A layer of an amorphous compound contg. Ca and/or Mn as the principal component such as calcium phosphate is then formed on the upper layer. The stripping of a paint film formed on the resulting surface treated steel sheet can be reduced, and performance necessary for a rustproof steel sheet for an automobile can be provided.