PRODUCTION OF DOUBLE-LAYER PLATED STEEL SHEET EXCELLENT IN ELECTRODEPOSITION COATING PROPERTY CAPABLE OF PREVENTING GENERATION OF BUBBLY DEFECT IN ELECTRODEPOSITION COATING FILM

摘要

PURPOSE:To produce a double-layered plated steel sheet excellent in electrodeposition coating property by successively forming a zinc-based plating film and an Fe-based plating film on the surface of a steel sheet respectively in a specified amt. and then heat-treating the steel sheet at a specified temp. CONSTITUTION:A single or double-layered plating film consisting of a Zn-based alloy plating and/or one or =2 kinds of Zn-based composite platings or a double-layered plating film consisting of a Zn-based alloy plating and/or one or =2 kinds of Zn-based composite platings and a Zn plating is formed on the surface of a steel sheet in the amt. of =25g/m2. An Fe plating and/or an Fe-based plating film consisting of one or =2 kinds of Fe-based alloy platings contg. =50% Fe are formed on the Zn-based plating film in the amt. of 1-10g/m2. The double-layered plated steel sheet is heat-treated at 100-400 deg.C for =1sec. Consequently, a rust-preventive steel sheet appropriate for the automobile is obtained.