| 摘要 |
PURPOSE:To improve the water resistance and secondary adhesion of a phosphate film formed on a galvanized steel sheet by previously treating the surface of the galvanized steel sheet with a treating soln. contg. specified amounts of an Fe compound and H3PO2 under specified conditions. CONSTITUTION:The surface of a galvanized steel sheet is treated with a treating soln. contg. 0.1-100g/l Fe compound and 1-100g/l H3PO2 at 10-50 deg.C for 1-60sec. FeCl2, FeSO4 or Fe(NO3)2 may be used as the Fe compound. An alloyed galvanized steel sheet having a Zn-Fe alloy layer, a Zn-Ni plated steel sheet, a Zn-Ni-Ti plated steel sheet or a Zn-Al plated steel sheet may be used in place of the galvanized steel sheet. A surfactant, a pH adjusting agent and a chelating agent may be added to the treating soln. The treated steel sheet is phosphated and painted by cationic electrodeposition. The painted steel sheet has high corrosion preventiveness and the paint film has high water resistance and secondary adhesion.
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