| 摘要 |
PROBLEM TO BE SOLVED: To provide a treatment method by which, when various kinds of metallic sheets having different sheet thicknesses are continuously passed through, the objective covering ratio of phosphate crystals can be obtained with high precision in any sheet thickness. SOLUTION: When metallic sheets having different sheet thicknesses to continuously be passed through are contacted with a phosphate treatment solution, and phosphate crystals are formed on the surfaces of the metallic sheets so as to obtain a covering ratio of <100%, the time of contact between the metallic sheets and the phosphate treatment solution is controlled in accordance with the sheet thicknesses of the metallic sheets.
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