Microstructure of Blackishgreen Passivation Film Based on Galvanized Steel Sheet

Environmental Friendly Zinc Coating was formed by the potassium chloride zinc plating handicraft. Above it, blackishgreen colored passivation film was prepared by dipping galvanized steel in solution made of foue types of acid with certain stabilizer and toner. SEM showed that the film was even and homogeneous. Zinc coating, passivation film and iron combined colsely, there weren´t microstructure defects such as cracks etc between them. The total thickness of zinc coating and passivation film reached 12.423μm, and blackishgreen colored passivation film was 1.734μm. XPS showed that there were Cr, O, P, N, Zn in the film, they probably existed in Cr(OH)₃, CrOOH, Cr₂O₃, ZnO, Zn₃(PO₄)₂·4H₂O, FeOOH, Fe (OH)₃ and Cr₂(SO₄)₃. XRD also showed that except the Zn crystal (zinc plating tier), other substances had appeared, they included CrPO₄, Cr(OH)₃, CrOOH, Cr₂O₃, Zn(OH)₂, 2ZnO·CrO₃·H₂O, Zn₃(PO₄)₂·4H₂O and Ag. In a word, the appearance of galvanized sample treated by the optimization passivation craft is blackishgreen, colour is uniform and lustre is gentle. Furthermore, this blackishgreen colored passivation craft has good effects in practical production.