Microstructure and corrosion behavior of FeCrNiCoMnx (x = 1.0, 0.6, 0.3, 0) high entropy alloys in 0.5 M H2SO4

The effect of Mn on the passivation behavior of FeCrNiCoMn high entropy alloy was elucidated in detail via anodic polarization of FeCrNiCoMnx (x = 1.0, 0.6, 0.3, 0) in 0.5 M H2SO4. A decrease in Mn content reduced Mn-related oxide/sulfide inclusions and elevated the Cr2O3 content in the passive film, conferring better corrosion resistance of FeCrNiCoMnx. The XPS results revealed a competitive oxidation of Mn with Cr, which lowered the Cr2O3 content in the passive film. This leads to inferior corrosion resistances of FeCrNiCoMn, FeCrNiCoMn0.6, and an equivalent resistance of FeCrNiCoMn0.3, compared to 304 L stainless steel.