Electrochemical Behavior of Hot-Dipped Zn-0.2Al-Mg-Re Alloy Coating on Steel Wire in NaC1 Solution

SEM, EDS and electrochemical measurements were used to investigate the structure and electrochemical characteristic of the hot-dipped Zn-0.2Al-Mg-Re alloy coating. The results indicated that the coating was composed of three layers: surface β-Zn sosoloid layer, middle 5 phase (FeZn₇) layer and inner Γ phase (Fe₅Zn₂₁) layer. There were three steps both in the constant current electrolysis corrosion curve and the corrosion potential curve of the coating in 5%NaCl solution, which showed that different phase layers of the coating had discrepant electrochemical characteristic. The corrosion potential of the coating in 5%NaCl solution increased from the surface to the inner phase layer. There was no obvious passive characteristic in the anodic polarization curve and the corrosion process was controlled by the reduction reaction of oxygen, which would probably be caused by the structure and corrosion products of the coating.