ELECTPLATING STEEL OF THE ZN-CR ALLOY WITH EXCELLENT CORROSION RESISTANCE AND METHOD THEREFOR

摘要

PURPOSE: An electroplated steel plate of zinc-chrome alloy having excellent corrosion resistance is provided, which is manufactured by controlling the deposit concentration for chrome of upper and under plated layers of zinc-chrome alloy by changing electric current density and composition of the plating solution. CONSTITUTION: The electroplating method is as follows: (i) continuously electroplate steel plate with zinc-chrome alloy in a plating solution of 30-60 g per liter of zinc and 20-40 g per liter of chrome, the concentration ratio of zinc-chrome being ≤ 1; (ii) form on the steel plate a zinc-chrome alloy plating layer of less than 4.5 wt.% of chrome deposition by current density of 20-60 A per square meter; (iii) and form on the alloy plating layer a zinc-chrome alloy plating layer of 4.5-12.8 wt.% of chrome deposition by current density of 60-100 A per square meter, the concentration ratio of chrome to zinc being ≤1.