Corrosion behavior and surface characterization of an equiatomic CoCrFeMoNi high-entropy alloy under various pH conditions

The corrosion behavior and surface characterization of an equiatomic CoCrFeMoNi high-entropy alloy (HEA) under various pH conditions were investigated by Mott-Schottky measurements, EIS, polarization, and XPS. The results showed that the passive films formed on the HEA displayed the n-p heterojunction electronic structure due to the generation of different semiconducting constituents. As the pH increased, the donor density decreased, which was attributed to the acceleration in the annihilation rate of the oxygen vacancies. Cr and Mo species were stable and were found enriched in the passive films, while substances of Co, Fe and Ni were depleted, independent of pH. Co and Ni mainly existed in the films in their metallic forms, both of which contributed less to the passive film formation. The stability of Fe was markedly enhanced with the pH increasing, resulting in the main components of the passive films changing from Cr and Mo to Cr, Fe and Mo. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The stability of passive films on the high-entropy alloy was influenced by species stability and vacancy concentration, with the stability of Fe increasing as pH rose.