Effect of Cr Addition on the Corrosion Behavior of Twinning-Induced Plasticity Steel

High-Mn austenitic Fe-Mn-C twinning-induced plasticity (TWIP) steels are prospective candidates in many industrial fields, owing to their excellent mechanical properties. However, these steels show poor corrosion resistance, which affects their performance and prevents their applications particularly in aqueous environment. In this study, an effective way to improve the corrosion resistant property of TWIP steels was described by understanding the corrosion behavior of TWIP steel that was alloyed with Cr. A series of Fe-25Mn-xCr-0.3C (x = 0, 3, 6, 9, and 12, mass fraction, %) TWIP steels were prepared in a vacuum arc melting furnace using high purity raw materials (>= 99.8%). Thereafter, the resulting steels were solution treated at 1200 degrees C for 2 h under an argon atmosphere. The effect of Cr addition on the corrosion behavior of the prepared TWIP steels was investigated using various analytical techniques including XRD, potentiodynamic polarization, electrochemical impedance spectroscopy, and XPS. XRD results showed that the TWIP steels with Cr content that ranged from 3% to 12% retained their single austenite phase. Moreover, increasing the concentration of Cr in the alloys substantially increased and decreased the corrosion potential and corrosion current density, respectively. These resulted in an improvement in the corrosion resistant property of the alloys, which was verified by the increase in the charge transfer resistance found in the Nyquist plots. Meanwhile, XPS results revealed that the prepared quasi-passive oxide film was composed of FeO, Fe2O3, FeOOH, MnO, MnO2, Cr2O3, and Cr(OH)(3). Furthermore, these results showed the progressive enrichment of Cr oxides and decrease of both Fe and Mn oxides in the outermost oxide as the Cr content was increased. The improved corrosion resistance of the prepared TWIP steels was caused by the protective Cr oxide film.