| 摘要 |
PROBLEM TO BE SOLVED: To provide a treatment method for a hot-rolled steel sheet or a steel material, which can form a dense and uniform zinc phosphate coating with adequate coating weight, and can exhibit a superior anticorrosion property, when treating the hot-rolled steel sheet or the steel material with a zinc phosphate treatment agent. SOLUTION: The treatment method for the hot-rolled steel sheet or the steel material, is characterized by treating the hot-rolled steel sheet or the steel material with the zinc phosphate treatment agent, which contains zinc ions of 0.5-3 g/l, manganese ions of 0.1-3 g/l, nickel ions of 0.1-4 g/l, phosphate ions of 5-40 g/l, nitric acid ions of 0.1-15 g/l, nitrous acid ions of 0.01-0.5 g/l, complex fluoride of 0.5-1 g/l as fluorine, and an organic chelate compound of iron of 0.005-0.1 g/l as iron, and/or an organic chelating agent which can be chelate bonded with ferrous ions of 0.025-0.5 g/l.
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