Alternatives for chromate conversion coatings for electrogalvanized steel sheet having a good appereance and corrosion resistance

摘要

PURPOSE: A method for manufacturing an electrogalvanized strip by using an alternative solution for Cr-free electrogalvanized strip having superior corrosion resistance without chromate treatment on the surface of the electrogalvanized strip is provided. CONSTITUTION: The method is characterized in that the surface of the electrogalvanized strip is treated with a Cr-free solution so that a coating film having superior corrosion resistance and beautiful external appearance is formed by reaction of the strip with galvanizing layer, wherein the Cr-free solution is prepared by preparing an acidic solution having pH of 0.5 to 2.5 and concentration of 0.05 to 0.2 mg/L by mixing one or more of metallic materials selected from alumina, phosphate and molybdenum to obtain superior reactivity of zinc with strip and superior corrosion resistance of the strip even at an ordinary low operation temperature, and sequentially adding 0.02 to 0.10 vol.% of tetraethylsilicate and 2 to 10 wt.% of urethane resin that is an organic polymer to the acidic solution.