PRECOAT STEEL SHEET EXCELLENT IN HARDNESS, PROCESSABILITY AND CORROSION RESISTANCE, AND PRODUCTION THEREOF

摘要

PROBLEM TO BE SOLVED: To enhance hardness and corrosion resistance by forming a topcoat film by applying a coating compsn. based on a compd. represented by a specific chemical formula and adding a polyester compd., polyol and a curing agent to a resin solid in specific wt. ratios and adding specific strontium chromate to an undercoat film. SOLUTION: A topcoat film is composed of 1-18 wt.% of a resin solid of a polyester compd. containing a main repeating unit represented by specific chemical formula [wherein n is an integer of 2-10; R is (CH2 )-m (wherein m is 1-10) and R' is 1,4-cyclohexane carboxylic acid]. As polyol, 40-90 wt.% of the resin solid of an acrylic resin or a polyester resin is used. As a curing agent, 9-50 wt. % of a blocked polyisocyanate compd. or an amino resin is used. Further, the content of strontium chromate added to an under coat film is set to 0.06-0.26 g/m<2> per film thickness of 1μm. By this constitution, hardness, corrosion resistance or the like can be enhanced.