PRECOATED STEEL SHEET WITH EXCELLENT HARDNESS, PROCESSABILITY AND CORROSION RESISTANCE AND ITS PREPARATION

摘要

PROBLEM TO BE SOLVED: To obtain a precoated steel sheet which exhibits a high coating film hardness and has excellent processability on severe molding processing and exhibits excellent corrosion resistance in environment in use after processing. SOLUTION: A precoated steel sheet with an undercoat coating film and a topcoat coating film on the surface of a galvanized sheet metal treated with a formation treatment in which the topcoat coating film is a coating film formed by applying a coating compsn. comprising 1-15 wt.% polyester compd. (l) with a main repeated unit of formula, 40-90 wt.% polyol (2) except (1) and 9-50 wt.% curing agent as main ingredients and the undercoat coating film contg. 0.06-0.26 g/m<2> strontium chromate per 1μm film thickness, is provided.