Microstructure and Corrosion Resistance of Hot Dip Zn-Sn-Ni Alloy Coatings

In this paper,0.36% silicon-containing steels were used and the growth dynamics and microstructure of hot dip galvanized Zn-Sn-Ni(w_Ni ≤ 0.12%,w_Sn=1%) coating of those steels at 450℃ were studied in a series of galvanizing experiments and by various of testing methods such as SEM,electrochemical polarization and XRD.The results showed that the Zn-Sn-Ni alloy bath method can effectively restrain the over-growth of galvanized coatings of reactive steels and gain eligible coatings with proper thickness,and compact microstructure.The corrosion rate of Zn-Sn-Ni coating is less than that of pure zinc coating in 5% NaCl solution.Zn-Sn-Ni coating shows lower corrosion current,the increasing polarization resistance,and presents the better corrosion resistance than pure zinc coating.The corrosion products of Zn-Sn-Ni and pure zinc coating are both composed of Zn₅(OH)₈Cl₂·H₂O and ZnO.