PRETREATMENT SOLUTION FOR CHROMATE COATING AND COATING METHOD OF ELECTROLYTIC GALVANIZED IRON USING THE SAME

摘要

PURPOSE: A pretreatment solution for chromate coating is provided to remove ZnO from the surface of an electrolytic galvanized iron with a pretreatment solution containing sulfuric acid, nitric acid and CrO prior to forming Zn-Cr-O chromate base coating. CONSTITUTION: The method for forming chromate coating on electrolytic galvanized iron includes: (i) dipping an electrolytic galvanized iron in a pretreatment solution containing CrO 3-10g/L, sulfuric acid 5-20g/L, and nitric acid 10-25g/L at a temperature range of 40 to 50deg.C for 3-10sec; (ii) roll coating the treated electrolytic galvanized iron with a chromate solution.