| 摘要 |
PROBLEM TO BE SOLVED: To improve an alkaline cleaning treatment performed as a pretreatment process for electrogalvanization of a steel sheet to be electroigalvanized and to enhance and stabilize appearance quality of an electrogalvanized steel sheet product. SOLUTION: The alkaline cleaning treatment performed as this pretreatment process comprises: using an alkaline cleaning solution Specified so as to have <=1.0% oil concentration, <=500 ppm iron concentration and <=50 ppm zinc concentration; introducing the alkaline cleaning solution S from an alkaline cleaning treatment section 10 having electrolytic degreasing vessel 11 and an alkaline scrubber vessel 12 into a regeneration treatment section 20; and at an appropriate time, repeatedly performing regeneration treatment that comprises subjecting the cleaning solution S to treatment using an oil removal device 21, an iron removal device 22 and a zinc removal device 23 successively and thereafter, returning the regenerated alkaline cleaning solution S to the alkaline cleaning treatment section 10, so that the contaminant concentration in the cleaning solution S is kept at an allowable value or lower to efficiently perform the prescribed pretreatment.
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