| 摘要 |
PROBLEM TO BE SOLVED: To obtain punching - and pressure mark-proof properties by providing a specific metal film on the surface of steel plate with specific plating, forming a chromate composition with a specified Cr deposition amount on the metal film, and further, forming a top film on a top layer or specific rust inhibitive pigment and co-pigment. SOLUTION: A metal film of at least, one type of element selected from among Ni, Co, Fe, Zr, Sb, V, Mo and W is formed on the surface of a galvanized or fused Al-plated steel plate, and a chromate composition at a total Cr weight ratio of 10-50% of Cr<3+> and 0.5-2.0 of gas-phase silica having a primary average grain size of 3-50μm, is formed on the upper layer or the metal film. In this case, the total or deposition amount is 10-150mg/m<2> . In addition, a polyester resin-primer film consisting of 10-100 pts.wt. of a basic phosphite rust inhibitive pigment for 100 pts.wt. of resin and the weight ratio of 0.02-0.5 of organic phosphonate as co-pigment for the rust inhibitor, is formed on the upper layer of the chromate composition. In addition, a top film containing 30-90% it the solid weight ratio of melamine curable-type polyester resin with a glass transition point of 5-70 deg.C and an average molecular weight of 15000-50000 and 1-50% at the solid weight ratio of organic particles as an aggregate with a primary grain size of 2-50μm, and 1-5% at the solid weight ratio of polyethylene wax as lubricant with a melting point of 0-130 deg.C, is formed on the top layer.
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