METHOD FOR MANUFACTURING SURFACE TREATED STEEL SHEET WITH EXCELLENT CORROSION RESISTANCE AND WELDABILITY

摘要

PURPOSE: A method for electrodepositing Mg on the surface of galvanized steel sheet or galvannealed steel sheet to improve corrosion resistance and weldability is provided. CONSTITUTION: The method is characterized in that steel sheet, galvanized steel sheet or zinc based alloy plated steel sheet is plated in a plating solution including Mg ion in an amount of 10 to 100 g/L under the conditions that the temperature of the plating solution is in the range of ambient temperature to 60 deg.C, pH 3 to 10 and the current density of the plating solution is 5 to 100 A/dm¬2; Mg is coated on the steel sheets in an amount of 0.05 to 2 g/m¬2; and further an organic resin coat is formed on the Mg oxide coat in an amount of 0.5 to 3 g/m¬2.