PRODUCTION OF DOUBLE LAYER PLATED STEEL SHEET HAVING SUPERIOR COVERING PROPERTY OF UPPER IRON-BASED ELECTROPLATING AND SUPERIOR POWDERING RESISTANCE

摘要

PURPOSE:To improve the throwing power and covering property of Fe-based electroplating formed on alloyed molten Zn plating by previously subjecting the Zn plating to cathodic electrolysis in a weak alkali soln. of a prescribed pH. CONSTITUTION:Alloyed molten Zn plating is formed on a steel sheet, the surface of this Zn plated steel sheet is subjected to cathodic electrolysis in a weak alkali soln. of pH8-12 and then Fe-based electroplating is formed on the treated Zn plated steel sheet. Superior covering property is ensured and powdering resistance by which plating layer is prevented from peeling at the time of press working is improved.