| 摘要 |
PROBLEM TO BE SOLVED: To obtain a surface treated steel plate for a highly corrosion resistant fuel tank which has excellent post-processing fuel corrosion resistance capable of withstanding the fuel, such as deteriorated gasoline and gasohol, with which the formic acid concentration is as high as 3000 providingm, and outer surface corrosion resistance and does not entail a cost increase while having excellent weldability. SOLUTION: (1) A Zn-X alloy copper electroplating film (one or >=2 kinds of 3 to 18 mass % Ni, 0.02 to 3 mass % Co, 25 to 45 mass % Mn and 8 to 29 mass % Cr) of 10 to 40 g/m2 in coating weight per one face and (2) a chromate film of 20 to 150 mg/m2 in coating weight in terms of metal Cr and (3) a baked coating film containing 10 to 30 mass % resin component consisting of a mixture composed of an epoxy resin and a phenolic resin at 90/10 to 60/40 by weight, 5 to 30 mass % polyolefinic wax, 20 to 70 mass % iron phosphide and 1 to 10 mass % strontium chromate and having a film thickness of 2.0 go 5.0μm are formed, successively from a lower side, on the steel plate.
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