Effect of Potential on the Characteristics of Passive Film on a CoCrFeMnNi High-Entropy Alloy in Carbonate/Bicarbonate Solution

Effect of passive potential on the protective capacity of passive film formed on CoCrFeMnNi high-entropy alloy was investigated in carbonate/bicarbonate solution by using electrochemical measurements, atomic force microscopy and x-ray photoelectron spectroscopy (XPS). The results reveal that the protective ability of passive film is sensitive to the applied potential, and the anti-corrosion property of passive film at high potential is significantly enhanced as indicated by the high film resistance and the low donor densities. The Cr 2 O 3 content and the ratios of Mn/Mn ox as well as O 2− /OH − in the secondary passive film are greater than those in the primary passive film. Moreover, increasing the potential facilitates the formation of a homogeneous and thick passive film, which considerably improves the protective ability of the film.