Effects of Trace Er on Microstructure and Properties of Hot-dip Galvanized Coating for Automobile

Hot dip galvanized coatings with different Er content were prepared on the surface of automobile steel by hot dip plating. The effects of Er content on the microstructure, hardness, thickness and corrosion resistance of the coatings were studied. The results showed that the average grain size of the coating decreased first and then increased with the increase of Er content, the minimum grain size could be obtained when Er content was 0.10%, and the surface quality could be improved with the addition of appropriate Er content. The average surface hardness of the coatings with different Er content was higher than that of Zn-0.6Al-0Er alloy coating, with the increase of Er content, the surface hardness of the coating increased first and then decreased, when the Er content was 0.10%, the maximum hardness was obtained, while the thickness of the coating decreased with the increase of Er content. With the increase of Er content, the average corrosion rate of the coatings decreased first and then increased, and Zn-0.6Al-0.10Er alloy coating had the best corrosion resistance.