Effect of Chromium Content on the Corrosion Performance of Fe-22mn-0.6c Twip Steels in Sulfate-Containing Environments

Abstract

This study investigates the influence of chromium additions (5 wt.-% and 10 wt.-%) on the corrosion resistance of Fe-22Mn-0.6C TWIP steels in aerated 0.1 M Na2SO4 at 25 °C. Microstructural and phase analyses were conducted using optical microscopy and X-ray diffraction, while corrosion products were characterized by SEM/EDS and Raman spectroscopy. Electrochemical techniques, including open circuit potential, linear sweep voltammetry, and electrochemical impedance spectroscopy, were used to evaluate passive oxide layer formation over 28 days. The results indicate that chromium additions significantly enhance corrosion resistance and improve steel passivation by promoting the formation of a stable, Cr-enriched oxide layer, resulting in more noble open circuit potential values, lower double-layer capacitance, and higher impedance. SEM and Raman analyses confirmed the presence of compact, adherent oxide layers enriched with α-FeOOH and FeCr2O4, which improved corrosion resistance. However, localized oxide delamination observed after prolonged exposure suggests that passive oxide layer stability may degrade over time. The insights obtained deepen the current understanding of passivation behavior in TWIP steels and highlight the critical role of chromium content in tailoring corrosion resistance under industrially relevant sulfate environments.

Keywords: TWIP steel, corrosion, passivation, chromium, electrochemical impedance spectroscopy