Electrochemical corrosion behaviour of oxide dispersion strengthened iron aluminides in 3.5 wt % NaCl solution

Abstract

Electrochemical corrosion and passivation characteristics of the oxide dispersion strengthened (ODS) Fe3Al–Ti and ODS Fe3Al–Ti–Zr alloys immersed for different exposure times of 1, 72, 120, 166 and 240 h in 3.5 wt % NaCl solution were studied using open-circuit potential, cyclic polarization and electrochemical impedance spectroscopy techniques. Both ODS Fe3Al–Ti and ODS Fe3Al–Ti–Zr alloys exhibit pitting corrosion under chloride ions exposure. In both alloys, corrosion rate decreased as immersion time increased and decreased beyond 72 h and similarly up to 240 h due to the formation of a passive layer that prevented further corrosion. ODS Fe3Al–Ti–Zr alloy exhibited more resistance to pitting corrosion for all exposure times than ODS Fe3Al–Ti alloy. Electrochemical impedance spectroscopy results indicated that the presence of Zr in ODS Fe3Al–Ti–Zr alloy improved the corrosion resistance, charge transfer resistance and its passive layer stability which can be attributed to the formation of a better protective passive layer as compared to ODS Fe3Al–Ti alloy. Even though the ODS Fe3Al–Ti–Zr alloy exhibited better passivation characteristics and corrosion resistance, the difference in electrochemical properties of the two alloys was marginal.