| 摘要 |
PURPOSE: A method for manufacturing zero spangle hot dip galvanized steel sheets with excellent surface gloss and appearance is provided, which is characterized in that after a solution for inhibiting the growth of spangle on hot dip galvanized steel sheets is sprayed onto the hot dip galvanized steel sheets, the solution is recovered and then chemically adjusted to reuse. CONSTITUTION: In a method for manufacturing zero spangle hot dip galvanized steel sheets with excellent surface gloss and appearance where ammonium phosphate solution is sprayed on a hip dip galvanized steel sheet and then the ammonium phosphate solution after recovery is again sprayed on the hip dip galvanized steel sheet, the method is characterized in that ammonium hydroxide (NH4OH) is added to the waste ammonium phosphate solution so that phosphoric acid (H3PO4) in the waste ammonium phosphate solution is reduced by monoammonium phosphate (NH4H2PO4); zinc monohydrogen phosphate (ZnHPO4) is precipitated in the form of (Zn(OH)2); and the waste ammonium phosphate solution is sprayed again on the hip dip galvanized steel sheet after reduction by monoammonium phosphate (NH4H2PO4).
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