Short-term formation kinetics of the continuous galvanizing inhibition layer on Mn-containing steels

Small additions of aluminum to the galvanizing bath results in improved coating ductility and adhesion through the formation of an Fe-Al interfacial (inhibition) layer which retards the formation of Fe-Zn intermetallic compounds. Understanding the interfacial layer formation mechanism, kinetics, and composition is very important in that it leads to better management of the galvanizing process and higher quality products. However, fundamental knowledge concerning this reaction is scarce and there is virtually no information on how this process functions in the case of Mn-containing advanced high-strength steels where a selectively oxidized MnO layer is present. In the present research, the effect of steel Mn content and reaction time (i.e. the sum of the dipping and overlay solidification times) on the formation kinetics and microstructural evolution of the inhibition layer in 0.20wt% dissolved Al bath were investigated. The results of Mn selective oxidation experiments and their effect on inhibition layer formation will be discussed.