Effect of Ce on the pitting corrosion resistance of non-equiatomic high-entropy alloy Fe40Mn20Cr20Ni20 in 3.5wt% NaCl solution

Abstract

This study focuses on the corrosion resistance of non-equiatomic Fe 40 Mn 20 Cr 20 Ni 20 high entropy alloys (HEAs) with addition of various cerium (Ce) concentrations in 3.5 wt% NaCl solution. The results of potentiodynamic polarization tests demonstrated that cerium can improve the pitting resistance of the HEAs in a considerable manner. Notably, the critical pitting potential ( E pit ) of samples increased dramatically with the addition of cerium, from − 58 mV SCE without cerium to + 265 mV SCE with 0.15 at% cerium in 3.5 wt% NaCl solution. Further the potentiodynamic polarization measures suggested that the impact of cerium addition on the pitting resistance of Fe 40 Mn 20 Cr 20 Ni 20 HEAs is not sensible to the salt concentration. In addition, electrochemical impedance spectroscopy (EIS) and Mott-Schottky tests showed that the addition of rare earth cerium led to the increase of the passive film thickness and the reduction of the donor density in the passive film, which partly accounts for the observed enhanced pitting resistance of the HEAs. • Adding cerium can effectively improve the pitting resistance of Fe 40 Mn 20 Cr 20 Ni 20 HEAs. • The thickness of passive film formed on the HEAs increase with addition of cerium. • The passive film formed on the HEAs with cerium is more protective than Ce-free HEAs.