Reactive wetting and in-situ aluminothermic reduction of Mn oxides in continuous galvanizing baths

The aluminothermic reduction mechanism was studied by galvanizing simulation using a dual-phase steel with 5.1 wt %. Mn. Annealing was carried out in Zn-0.2 wt% dissolved Al bath at 630 and 770°C for 120 to 2400 s and the surface chemistry and morphology prior to dipping analyzed and the coating quality characterized. Mn segregation to the surface and oxidation was observed for all the annealing conditions and a thick (~ 0.6 μ) Mn oxide film was formed by annealing at 770°C for 2400 s. The in situ aluminothermic reduction of MnO by bath dissolved Al was characterized by relating the pre-dipping interfacial structure to the post-dipping structures using a variety of characterization techniques. The validity of this postulated mechanism of oxide reduction by the dissolved Al in the continuous galvanizing bath will be discussed based on the results of this investigation.