ZN-CR-SN-BASED ORGANIC COMPOSITE PLATED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE AFTER WORKING, CORROSION RESISTANCE OF COATING AND RUST PREVENTING PROPERTY OF END FACE

摘要

PURPOSE:To provide a Zn-Cr-Sn-based org. composite plated steel sheet excellent in corrosion resistance after working, corrosion resistance of the coating and rust preventing property of the end face. CONSTITUTION:This org. composite plated steel sheet has the electroplating layer of a Zn-Cr-Sn-based alloy contg. 7-15% Cr, 0.3-1.2% Sn and the balance Zn, a chromate layer is formed thereon by electrolysis or coating, and further an org. resin coat is formed thereon. An excellent chromate film is formed by limiting the Cr and Sn contents, corrosion resistance is improved, and the adhesion to the org. film is secured. The plating layer is not broken in working, excellent corrosion resistance is maintained even after working, the sacrifice corrosion prevention is also secured, and hence an org. composite steel sheet excellent in characteristics is produced by using the alloy plating as the substrate. An excellent rust prevention steel sheet for the car body is produced in this way.