| abstract |
Organic composite coated steel strips having improved corrosion resistance, weldability and coating adherence are obtained when an organic composite layer is applied to a chromate layer on a zinc or zinc base alloy plated steel substrate. The chromate layer containing up to 70% of Cr6+based on the total chromium weight is coated in a weight of 5 to 500 mg/m2 of Cr. The organic composite layer is formed to a dry weight of 0.2 to 3.0 g/m2 from a coating composition comprising (A) a silica sol having silica dispersed in an organic solvent with a water content of up to 3.0%, the silica having an organic deposit on its surface in an amount of up to 5.0% of C based on the total silica weight, the silica having an average particle size of 0.05 to 3.0 (my)m and a specific surface area of 50 to 800 m2/g, and (B) an organic resin binder having a number average molecular weight of at least 2,000. The coated strips are suitable for use as automobile bodies by press forming. |