METHOD FOR ELECTROPLATING OF THE ZN-CR-FE ALLOY WITH HIGH CORROSION RESISTANCE AFTER COATING AND METAL SHEET USED THEREFOR

摘要

PURPOSE: An electroplated steel plate of zinc-chrome-iron alloy having excellent corrosion resistance after painting is provided, which is manufactured by controlling the deposit concentration for chrome and iron of upper and under plated layers of zinc-chrome-iron alloy by changing electric current density and composition of plating solution. CONSTITUTION: The electroplated steel plate is as follows: (i) an under plated layer of zinc-iron alloy that has less than 4.4-7.9 wt.% of chrome deposition and less than 9 wt.% of iron deposition; and (ii) an upper plated layer of zinc-chrome-iron alloy that has less than 4 wt.% of chrome deposition and 10-80 wt.% of iron deposition, the upper plated layer having attached amount of 1-5 g per square meter.