A Comparison Between Corrosion Behaviors of Fine-Grained and Coarse-Grained Structures of High-Mn Steel in NaCl Solution

In this study, a fine-grained structure was obtained in high-Mn austenitic steel through martensite treatment. The corrosion response of fine-grained and coarse-grained steels was studied and compared in 3.5 wt.% NaCl solution. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and Mott-Schottky analysis were performed to understand the effect of grain refinement on the electrochemical behavior of this steel. Microstructural evaluation showed that by reduction in grain size, the amount of low energy grain boundaries was increased, which led to better electrochemical behavior. In addition, the corrosion resistance of fine-grained steel did not deteriorate in comparison with coarse-grained steel. Both specimens showed a charge-transfer resistance of about 4-5 k Omega cm(2) in NaCl. Besides, a protective film related to fine-grained sample was detected by EIS and Mott-Schottky analysis, which could be a sign of higher grain boundaries in this steel.