| 摘要 |
PROBLEM TO BE SOLVED: To provide a precoated steel plate capable of obtaining excellent properties in addition to worked part corrosion resistance without adding a chrome-based rust proofing pigment into a coating film. SOLUTION: An under coating film containing 5-50 pts. wt. calcium ion- exchanged silica per 100 pts. wt. resin solid matter is formed on the surface of a galvanized steel sheet on which a chemically converted coating film containing silica fine particles and a binder therefor is formed and a top coating film is formed on the upper layer thereof by applying a coating material composition containing the following (a) to (c) as resin solid matter in a prescribed ratio. (a) is a polyester compound composed of a repeating unit expressed by general formula 1 (in formula 1, (n) represents integers of 2-10, R represents polyoxymethylene group, 1, 4-cyclohexylene dimethyl group, neopentyl group or (CH2)m (m=1-10) and R' represents a group expressed by formula 2 or formula 3, (b) is a pololyester resin and/or an acrylic resin and (c) is an isocyanate compound and/or an amino resin as a hardening agent.
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