On the reactive wetting of Fe-Mn-Sb alloys during continuous hot-dip galvanizing

The effect of a Sb micro addition on the reactive wetting of Fe-(2−10)Mn-(0.00/0.03)Sb (at. pct) by a Zn(Al,Fe) galvanizing bath was determined. Despite the presence of surface oxides prior to immersion, an integral zinc coating was obtained on all Fe-Mn-Sb steel substrates. It was found that Sb segregation at the external oxide/substrate interface resulted in a decrease in the size of the external oxide particles, which facilitated contact between the Zn bath and the substrate. Moreover, it was determined the size of the closely packed FeAl intermetallics at the coating/steel interface increased as a result of adding Sb to the steel, which was attributed to the finer and thinner external oxide particles formed on the surface of these steel prior to dipping and lower stability of the oxide/substrate interface, which allowed for facilitating the advancement of reactive wetting occurred through mechanisms such as the aluminothermic reduction of MnO, oxide bridging, and oxide lift-off. In addition, a mechanism for the efficacy of Sb as a surface-active element during the continuous galvanizing process was determined. The analysis revealed that the segregated Sb dissolved into the liquid Zn and disrupted the oxide bond with the substrate. This can be attributed to Sb higher electronegativity with Zn compared to Fe and its sufficient solubility in liquid Zn at 460 °C. After the formation of the desired interfacial layer, no Sb segregation was observed at the interface between the interfacial layer and the substrate. These results highlight the considerable advantages of applying a Sb micro-addition for enhancing the reactive wetting of AHSSs with higher Mn contents in the continuous galvanizing process.