Effect of nitric acid concentration on corrosion behavior of CrFeCoNi high entropy alloy

CrFeCoNi high entropy alloy (HEA) was prepared by the method of vacuum melting. Its corrosion behavior in HNO3 solution with different concentrations was studied. The electrochemical test results indicated that the corrosion resistance firstly increased with increasing HNO3 concentration from 0.1 M to 4 M, and then decreased with further increasing HNO3 concentration to 6 M. The CrFeCoNi HEA exhibited the best corrosion resistance in 4 M HNO3 solution. The discrepancy of corrosion property in different concentration of HNO3 solutions could be attributed to the different protection of passive film formed on HEA. XPS results indicated that the content of Cr2O3 in the passive film initially increased with increasing HNO3 concentration from 0.1 M to 4 M, and then decreased with further increasing HNO3 concentration to 6 M. Higher content of Cr2O3 in the passive film was responsible for better corrosion property. [Display omitted]