Effects of lanthanum addition on the microstructure and corrosion resistance of galvanized coating

Abstract Based on the test results of the La solubility in iron-saturated liquid zinc, the galvanized coatings with the unsaturated (0.006 wt%), saturated (0.012 wt%), and supersaturated (0.2 wt%) lanthanum (La) additions were prepared on mild steel surface in this study. The microstructure and corrosion resistance of coated specimens were studied by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), weight loss tests and electrochemical methods. These results illustrated that La partially dissolved in Zn. On the other hand, La reacted with Zn to form LaZn 13 and promoted the dendritic growth of coating. The weight loss of La-containing galvanized coatings decreased by 5–25% gradually due to the inhibition of cathodic reaction. The results of SKP indicated the number of micro cells decreased with the La addition.