The Fe-Zn-Al-Cr system and its impact on the galvanizing process in chromium-added zinc baths

The zinc rich corner of the Fe–Zn–Al–Cr at 460 °C is of interest for galvanizing because Al is a usual addition element in zinc bath, whereas Cr is naturally present because it is supplied by the stainless steel roller dipping in the Zn bath during the process. Indeed, it is used to understand the formation and growth mechanisms of the solid phases during galvanizing in Al and Cr-added Zn bath. By using additional experimental results in the Al–Cr–Zn and Fe–Zn–Al–Cr systems, the zinc rich corner of the Fe–Zn–Al–Cr system at 460 °C was determined with more accuracy. Thus, new equilibria between the liquid and quaternary phases have been pointed out, namely Al2Cr3 stabilized by Zn and enriched with Fe and τ1, the latter being isotypic with δ-FeZn9. This quaternary system was assessed with the CALPHAD method using the PARROT module of the Thermo-Calc Software. The liquid and solid solutions are described by the Redlich-Kister-Muggianu equations. All the modeled phases are considered as stoichiometric in the binary systems.