PRODUCTION PROCESS OF GALVANIZED STEEL SHEET

PROBLEM TO BE SOLVED: To establish galvanization conditions effecting high rust inhibitory performance of a galvanized coating layer by appropriately controlling the temperature, pH, current density and galvanized coating layer thickness in an electrolytic solution consisting of a zinc sulfate hydrate and ammonium sulfate, in a production process of a galvanized steel sheet. SOLUTION: This production process comprises: a pretreatment stage for cleaning and picking the surface of a steel sheet; a main stage for performing galvanization of the pretreated steel sheet by passing it through a galvanization cell; and a post-treatment stage consisting of cleaning, oiling and drying operations for the resulting treated steel sheet; wherein the pretreated steel sheet is passed through a galvanization electrolytic solution consisting of 87-97 wt.% of ZnSO4.8H2O and 3-14 wt.% of (NH4)2SO4 under conditions of 100-300 mA/cm2 current density, 48-52 deg.C temperature of the electrolytic solution and a pH value of the electrolytic solution of 3.5-4, to form a galvanized coating layer having a 5-7 μm thickness.