| 摘要 |
PROBLEM TO BE SOLVED: To obtain a preprimed galvanized steel sheet which satisfies coating film conditions specified by JIS K 5629 and has excellent workability, overcoating paint adhesive properties and corrosion resistance suitable as a fireproofing material. SOLUTION: A chemically treated film is formed on a galvanized steel sheet surface, and the surface is sequentially formed with a lower layer coating film containing resin content obtained by mixing 1 to 10 pts.wt. of epoxy resin and 5 to 30 pts.wt. of melamine resin with 100 pts.wt. of polyester resin having specific glass transition temperature and pigment and having the weight ratio of the resin to the pigment of 1:0.20 to 1:1.50 and an upper layer coating film containing resin content obtained by mixing 100 pts.wt. of polyester resin having specific glass transition temperature with 5 to 20 pts.wt. of epoxy resin and 5 to 30 pts.wt. of melamine resin, pigment and having the weight ratio of the resin to the pigment of 1:1.50 to 1:3.00 and the 20 to 40wt.% of the pigment in both the coating films is calcium plumbate.
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