PRODUCTION OF HOT DIP ZINC-ALUMINUM ALLOY PLATED STEEL SHEET HAVING SUPERIOR SURFACE SMOOTHNESS AND HIGH CORROSION RESISTANCE

摘要

PURPOSE:To produce a hot dip Zn-Al alloy plated steel sheet having superior surface smoothness and high corrosion resistance by hot dip plating a steel sheet in a Zn plating bath contg. specified amts. of Al, Si and Mg and a regulated total amt. of impurities at a specified low temp. of the bath. CONSTITUTION:A steel sheet is hot dip plated in a plating bath consisting of 3.0-10.0wt.% Al, 0.01-1.0wt.% Si, 0.05-1.0wt.% Mg, 0.02wt.%, in total, of inevitable impurities and the balance Zn at 480 deg.C temp. of the bath. Rapid cooling is preferably carried out at 50-300 deg.C/sec rate while the resulting plating layer is in a half-molten state immediately before solidification. A hot dip Zn-Al alloy plated steel sheet having spangle-free plated appearance, fine appearance after coating, superior corrosion resistance and adhesion of the plating layer is obtd.