Electrochemical corrosion behavior of nanostructured BCC-Al0.5CoCrFeNi0.4 high-entropy alloy in sodium chloride solution
(1. Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China;
2. National Materials Corrosion and Protection Data Center, University of Science and Technology Beijing, Beijing 100083, China)
2. National Materials Corrosion and Protection Data Center, University of Science and Technology Beijing, Beijing 100083, China)
Abstract: The electrochemical corrosion behavior of Al0.5CoCrFeNi0.4 high-entropy alloy (HEA) in 3.5 wt.% NaCl solution was investigated by electrochemical measurements coupled with comprehensive characterization of its surface films. The results demonstrate that the Al0.5CoCrFeNi0.4 HEA primarily consists of (Al,Ni)-rich B2 phase and (Cr,Fe)-rich A2 phase. When subjected to electrochemical polarization, an ultrathin passive film rich in Cr is homogeneously formed on the surface. As the applied potential increases, the protective film tends to break down at the interface of two phases, followed by the preferential dissolution of B2 phase. Finally, the surface film with a triple-layer structure is formed on the HEA surface. Specifically, the inner layer and the middle layer are enriched in Cr and Fe, respectively, due to the high stability of Cr species and the selective dissolution of Fe. The (Al,Ni)-rich corrosion products are found to deposit at the outmost position ascribed to the dissolution of B2 phase.
Key words: high-entropy alloy; electrochemical corrosion behavior; selective corrosion; transpassivation; triple-layer oxide film