| 摘要 |
PROBLEM TO BE SOLVED: To obtain punching - and pressure mark-proof properties by providing a specific metal film on the surface of a specifically plated steel plate, further, providing a chromate composition with a specified total Cr deposition amount on the metal film, and finally, forming a specific rust inhibitive pigment layer and a top film. SOLUTION: The 3-50mg/m<2> of a metal film consisting 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. In addition, a chromate composition at a total Cr weight ratio of 10-50% of Cr<3+> and 0.5-2.0 of gas-phase silica with a primary average grain size of 3-5μm is formed on the upper layer of the metal film. In this case, the total Cr deposition amount is 10-150mg/m<2> . Further, the 0.5-10μm of polyester resin primer film consisting of a blend of 10-100 pts.wt. of basic phosphite rust inhibitive pigment with 100 pts.wt. of resin, is formed on the upper layer of the chromate composition. on the top layer, a top film containing 30-90% at the solid weight ratio of a melamine curable polyester resin with a glass transition point of 5-70 deg.C and an average molecular weight of 15000-50000, 1-50% at the solid weight ratio of organic resin particles as an aggregate with a primary average grain size of 2-50μm, and 1-5% at the solid weight ratio of polyethylene wax with a melting point of 80-130 deg.C as a lubricant, is formed.
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