Unveiling the underlying corrosion/corrosion-resistance mechanism of a novel corrosion-resistant high entropy alloy by experimental means and AIMD simulations

In this work, we designed a new corrosion resistant high entropy alloy (CR-HEA) FeCoCrNiMo0.1Nb0.1. Its microstructure, corrosion behavior and passive film properties were studied by micro-characterization and electrochemical tests. The corrosion/corrosion-resistance mechanism was further revealed by first-principles calculations at atomic level. It is found that the designed HEA consists of (Mo, Nb)-lean FCC phase and (Mo, Nb)-rich Laves phase. Due to the formation of compact and protective passive film, our HEA exhibits a superior comprehensive corrosion resistance in the H2SO4 solution. AIMD and DFT calculations indicate that corrosive species are more likely to adsorb on the FCC phase, i.e., the FCC phase is preferentially attacked. Additionally, OH and O are easier to adsorb on Cr, Mo, and Nb atoms. Thus a more stable passive film is formed on the (Mo, Nb)-rich Laves phase, which provides better protection for Laves phase.