Effect of NiCl2-Based Fluxes on Interfacial Layer Formation of Hot Dip Galvanized Steels

While the thick growth of intermediate phase layers generally benefits the corrosion resistance of galvanized steels, it is unfavorable from the standpoints of mechanical integrity and economics. Thus, the influence of nickel chloride based fluxes and the typical zinc-ammonium chloride flux on galvanized coating thickness as well as coating morphology and composition is examined. The investigation of pretreated hot dip galvanized steel specimens for various durations has verified that nickel chloride fluxes influence the growth rate of the zeta interlayer. This results in the overall reduction of the coating thickness by as much as two times compared to those prepared with the conventional flux. Nickel from the fluxes gradually diffuses away from the substrate's surface, and hence the initial concentration of the nickel salts along with the hot dip duration needs to be controlled appropriately for effective use of nickel chloride-based fluxes in the galvanizing process.