DFT study on the mechanism of inclusion-induced initial pitting corrosion of Al-Ti-Ca complex deoxidized steel with Ce treatment.

Abstract The mechanism of inclusion-induced initial pitting corrosion of Al-Ti-Ca complex deoxidized steel with Ce treatment was studied by the experimental investigation and theoretical calculation. To figure out which phases of complex inclusion containing different components induced initial pitting corrosion, the scanning electron microscope (SEM) analysis, the continuous immersion experiments and density functional theory (DFT) calculation were conducted. Two types of inclusions and different pit morphologies were observed. The pit initially occurred at the sulfide inclusions (MnS and Ce 2 O 2 S) rather than the steel matrix due to the lower the electronic work function (EWF) of this compound compare to the steel matrix and other phases. In addition, the Ce-rich inclusion possessed the higher pitting corrosion resistance than the same type of inclusions. Finally, a schematic diagram was established to explain the mechanism of the different inclusions in initiating and proceeding pitting corrosion. Highlights • The xCaO-yAl 2 O 3 -TiN-MnS inclusions in Ce-free steel were modified to CeAlO 3 -Ce 2 O 2 S inclusions in the Ce-bearing steel. • The pitting corrosion initiates in the sulfide inclusions which have the lowest EWF in both steels. Besides, the Ce-rich inclusion, by contrast, had higher EWF than xCaO-yAl 2 O 3 -TiN-MnS inclusions. [ABSTRACT FROM AUTHOR]