Effect of Mg on Microstructure of Hot-dip Galvanized Zinc-based Alloy Coatings

Hot-dip galvanizing was used to prepare zinc-based alloys on the surface of Q235 steel sheet. The alloys contains various Mg contents of 0wt%, 0.1wt%, 0.3wt%, 0.5wt%, respectively. SEM, EDS and GDOES were used to analyze the effect of Mg content on the microstructure of alloys. The results show that with the increase of the content of Mg in the coating, the grain size of coating decreased. Mg segregated in grain boundaries and played a role of fining the grain size. Mg is capable of hindering the transformation of ζ phase to δ phase, resulting in thin δ phase layer.