Effect of Mn additions on the corrosion behaviour of TWIP Fe-Mn-Al-Si austenitic steel in chloride solution

Corrosion of TWIP austenitic steels Fe-Mn-3Al-3Si was studied using polarization curves, EIS tests and XPS. Results indicated that increased concentrations of Mn were detrimental to its corrosion resistance. XPS study revealed that pseudo-protective oxide layer was composed of FeO, Fe2O3, FeOOH, Al2O3, MnO and MnO2. Enrichment of Mn oxides in the outermost oxide layer was found as Mn increased in the TWIP steel bulk along with a decrease in Fe oxides. The increased corrosion susceptibility exhibited with the concentration of Mn in the alloys was associated with the greater contribution of the less protective Mn oxide in the surface film.