Comparative corrosion behavior of Fe50Mn30Co10Cr10 dual-phase high-entropy alloy and CoCrFeMnNi high-entropy alloy in 3.5 wt% NaCl solution

Abstract

Abstract The corrosion behavior of a Fe50Mn30Co10Cr10 dual-phase high-entropy alloy (DP-HEA) in NaCl solution was investigated in this study. All the corrosion results were compared with those of an equiatomic CoCrFeMnNi high-entropy alloy (HEA). The corrosion product films that formed on the surface of both alloys after immersion in NaCl for 14 days were directly imaged for the first time through high-resolution transmission electron microscopy (HR-TEM). Both of the alloys exhibited similar passivation and positive hysteresis processes in the potentiodynamic polarization test. However, the Fe50Mn30Co10Cr10 DP-HEA exhibited a narrower passive region and lower pitting potential (Epit) value compared with the CoCrFeMnNi HEA. Electrochemical impedance spectroscopy results suggested that the CoCrFeMnNi HEA has better corrosion resistance performance than the Fe50Mn30Co10Cr10 DP-HEA in a NaCl solution. HR-TEM observations indicated that the Fe50Mn30Co10Cr10 DP-HEA formed a thicker corrosion product film (∼12 nm vs ∼3 nm for the CoCrFeMnNi HEA) after it was immersed in NaCl solution for 14 days. Moreover, Auger electron spectroscopy results revealed that the corrosion product film on the Fe50Mn30Co10Cr10 DP-HEA contained higher Mn content and lower Cr and Fe content than the films on the CoCrFeMnNi HEAs.