Electrochemical polarization and pitting behaviour of Fe-Al-Mn alloys in chloride solutions

The electrochemical polarization behaviour of the austenitic Fe-8.25 Al-29.95 Mn-0.85 C and Fe-9.33 AI-25.94 Mn-1.45 C alloys, either solution-annealed and/or age-treated, was investigated in 3.5 wt% NaCl solution. Potentiodynamic polarization tests showed that these alloys passivated with difficulty and had much higher anodic passive current densities than that of the conventional austenitic 316 stainless steel (SS). The susceptibility to pitting corrosion of these alloys under open-circuit potential conditions was also studied in 6% FeCl₃ solution. Metallographical examination indicated that pitting and general corrosion occurred on the specimen surfaces. The corrosion rates of these alloys were about one order of magnitude higher than that of the AlSl 316 SS. In general, the corrosion resistances of the Fe-Al-Mn alloys studied were inferior to that of the conventional stainless steel./p]