Abstract The corrosion behavior and mechanism of a novel FeCrNi medium entropy alloy (MEA) prepared by powder metallurgy method in 3.5 wt% NaCl solution was investigated in this study. The results indicated that, compared with the 316L SS, the FeCrNi MEA exhibits outstanding corrosion resistance with a more positive breakdown potential (0.982 VSCE) and lower current density ( 8.317 × 10 − 8 A / c m 2 ). The passive film formed on the surface of the FeCrNi MEA is a Cr-riched and less defective film. At the same time, it also has a strong self-healing ability. Uniform microstructure and high Cr content are responsible for the good anti-corrosion performance.