Repassivation behaviour and surface analysis of Fe3Al based iron aluminide in 0.25 M H2SO4

The repassivation kinetics of iron aluminide having a composition of Fe-16Al-0.14C (wt.%) were investigated in 0.25 M H2SO4 along with pure Al and Fe using a rapid scratched electrode technique. The repassivation behaviour of iron aluminide demonstrated was faster compared with Al, whereas the repassivation behaviour of Fe was slower than Al despite having a lower passive current density than Al. The repassivation behaviour was analyzed in terms of current density [i/t] as a function of charge density [q/t] that flowed from the scratched surface based on high-field ion conduction model and surface chemistry of the passive film. A mechanistic model is presented to explain the passivation/repassivation behaviour of iron aluminide based on the new findings.