RUSTPROOF STEEL SHEET HAVING SUPERIOR SUITABILITY TO COATING BY ELECTRODEPOSITION

摘要

PURPOSE:To provide a rustproof steel sheet having superior corrosion resistance and suitability to coating by electrodeposition by forming an Al-Cr alloy layer contg. a specified wt. percentage of Cr on a steel sheet and further forming a coating film based on urethane resin and silicon dioxide. CONSTITUTION:An Al-Cr alloy plating layer contg. 5-30wt.% Cr is formed on a steel sheet and a coating film based on urethane resin and silicon dioxide is further formed on the plating layer optionally with a chromate layer in-between. In the coating film, the urethane resin and silicon dioxide are present as a compound substance formed by coupling with a silane coupling agent. A rustproof steel sheet having superior corrosion resistance and suitability to coating by electrodeposition can be provided.