| 摘要 |
PURPOSE:To considerably reduce the formation of GASPIN (pinhole-shaped defect) when a Zn-Fe alloy plated steel sheet used as a steel sheet for an automobile body is painted by cationic electrodeposition, by previously depositing a composition consisting of Fe-P, Fe and FeO on the surface of the steel sheet in a dispersed state. CONSTITUTION:A steel sheet having a delta1 phase-base Zn-Fe alloy layer formed by plating and used as a steel sheet for an automobile body is immersed in an aqueous soln. contg. 10-80g/l FeCl2 and 10-100g/l H3PO2 at 20-50 deg.C for 1-60sec to deposit a composition consisting of Fe-P, Fe and FeO on the surface of the steel sheet by 0.5-5g/m<2> in a dispersed state. The steel sheet is then degreased, phosphated, painted by cationic electrodeposition and dried by baking. The amount of GASPIN is extremely small and a steel sheet having superior resistance to corrosion by rock salt spread to prevent freezing of a road in the winter and salt particles in a coastal region is obtd. |
