RUSTPROOF STEEL SHEET

PURPOSE:To obtain a rustproof steel sheet in which the effective corrosion resistance is given for the appearance corrosion of outside surface and the perforation corrosion of inside surface by performing both the composite galvanizing on the outside surface of the steel sheet and the galvanizing or the composite valvanizing on the inside surface there of with different thickness. CONSTITUTION:A rustproof steel sheet is obtained by performing 5-15g/m composite galvanizing such as Zn-Ni alloy plating and Zn-Al alloy plating on the outside surface of the steel sheet and performing 20-45g/m galvanizing composite galvenizing on the inside surface thereof. In this rustproof steel sheet, the conposite galvanizing which is excellent in adhesive properties of the coated film and in finish coating quality is performed on the outside surface with the coated quantity effective for the appearance corrosion and the plated film having the quantity effective for the perforation corrosion is performed on the inside surface. The rustproof steel sheet can be effectively used as an outside sheet, a fender, a hoold and a door or the like of an automobile body.