Among those intermetallic phases in Zn-Fe system formed in the hot-dip galvanized coating and/or galvanneal coating, the microstructure of Γ phase was the least mentioned. The Γ phase form in the coating layer is usually too thin to observe by a microscope. However, it has been reported that the performance of coating is closely related to the microstructure of Γ phase. Tokunaga et al. has reported that the cracks were generated from the Γ layer or Γ+δ layer. Y.Lin et al. demonstrates that coherent interface forms between Γ and steel interface on annealed electrogalvanized steel sheets indicating that failure would not occur at this interface.Samples used in this study were lab-made hot-dip galvanized steel sheets. To investigate the microstructure of coating, especially the Γ phase layer, specimens were heated to create the designed layer interface. It was found that the heat-treated conditions ranged from 700°C to 750°C for one hour was appropriate to observe the nucleation and growth of Γ phase layer.
Correlation between the surface chemistry of annealed IF steels and the growth of a galvanneal coating
