Effects of the element La on the corrosion properties of CrMnFeNi high entropy alloys

The effect of minor inclusion of rare earth element of lanthanum into a well-established high entropy alloy system of CrMnFeNi on their corrosion resistance properties in different media with various concentrations was investigated in this study. The potentiodynamic polarization curves of the CrMnFeNi and CrMnFeNiLa0.1 alloys in acidic solutions exhibit an extensive passive region (ΔE>1100 mV). The Nyquist plot of the La-free CrMnFeNi alloy includes one capacitive loop and one inductive loop and while for the CrMnFeNiLa0.1 alloy only one capacitive loop is present. SEM results show that the morphology of the two alloys is obviously different in different media. XPS data reveals the existence of distinctive content discrepancy of Mn and Ni in passive film between La free and La-containing HEA, strongly implying the considerable impact of La in the passivation process.