ORGANIC COMPOSITE PLATED STEEL SHEET OF ZN-CR-CO SYSTEM HAVING EXCELLENT POST-WORKING CORROSION RESISTANCE, PAINTING CORROSION RESISTANCE AND END FACE RUST PREVENTING PROPERTY

摘要

PURPOSE:To provide the surface treated steel sheet having extremely high post-working corrosion resistance, post-painting corrosion resistance and end face rust preventing property. CONSTITUTION:This org. composite plated steel sheet has an electroplating layer of a Zn-Cr-Co alloy consisting of 6 to 15% Cr concn. and 0.3 to 1.0% Co concn. and the balance Zn, has a chromate layer thereon and is further coated with an org. resin thereon. The excellent chromate film is formed by limiting the contents of the Cr and Co to the above-mentioned range. In addition, the destruction of the plating layer by working is obviated and a sacrificial corrosion preventive effect is maintained. The org. composite plated steel sheet having the excellent characteristics is thus produced by using the alloy plating of the above-mentioned system as a substrate. The org. composite steel sheet having the extremely high post-working corrosion resistance, the post ED painting corrosion resistance and the end face rust preventing property is produced. This steel sheet is optimum for the rust preventive steel sheet of automobile bodies.