| 摘要 |
The present invention provides an organic composite plated steel sheet highly susceptible to cationic electrodeposition comprising a steel substrate plated with one selected from the group consisting of zinc, a zinc alloy, a zinc composite alloy, or aluminum, and a first layer of a less soluble chromate film having a water soluble content of 5% or less formed on the substrate in an amount of 10 to 150 mg as the total amount of chromium per square meter, and a second layer as a solid thin coating film of 0.2 to 2 mu m formed on the first layer, the second layer being formed with a coating composition containing 10 to 50% by weight of solids comprising: (a) 30% by weight or more of a bisphenol A type epoxy resin having a number average molecular weight of 300 to 100,000 based on the total solids in the coating composition; (b) a weight ratio of at least one curing agent selected from the group consisting of polyisocyanate compounds and block polyisocyanate compounds to the epoxy resin solid of 0.1 to 2.0; (c) 5 to 50% by weight of fumed silica having an average particle size of 0.1 to 100 nm based on the total solids in said coating composition; (d) at least one pigment selected from the group consisting of insoluble azo type, azo lake type, and phthalocyanine type organic pigments having an average size of 0.01 to 2 mu m in an amount of 0.1 to 15% by weight based on the total solids in the coating composition and in a weight ratio of the pigment to the fumed silica of 0.01 to 1.0; and (e) 40% or more of a ketone type organic solvent in the coating composition. o |
