Effect of process variables on the solidification of hot-dip galvanized coatings

Continuous hot-dip galvanizing is a common industrial process in which steel sheet is immersed in a molten zinc bath in order to form a corrosion resistant zinc-based coating on the steel surface. Small amounts of antimony are sometimes added to the galvanizing bath to reduce zinc viscosity and ease the gas jet wiping operation. The current study investigates the influence of process variables such as bath composition, steel surface roughness and cooling conditions on the solidification and microstructure of zinc coatings. It was found that small antimony additions have a strong influence on the microstructure of the metallic coating through its effect on the melt surface tension. It was also found that the substrate roughness had a strong influence on the preferred orientation of the Zn crystals. The effect of all experimental variables on the resultant microstructure of the zinc coatings will be discussed.