Microstructure and corrosion properties of Cr41CoFeNi eutectic high-entropy alloy in sulfuric acid solution

A new eutectic high-entropy alloy (EHEA) of Cr41CoFeNi was prepared by arc melting technique. The microstructure and corrosion resistance of the Cr41CoFeNi EHEA were systematically investigated by EBSD, TEM, EIS and XPS analyses. The results revealed that the Cr41CoFeNi EHEA showed a dual-phase structure consisting of BCC phase and FCC phase, and the morphologies displayed the lamellar eutectic and network-shaped eutectic. Compared with 316 L stainless steel, the Cr41CoFeNi EHEA exhibited a better anti-corrosion property in 0.5 M H2SO4 solution. This was mainly attributed to the formation of a dense and stable Cr-oxide layer on the surface of Cr41CoFeNi EHEA, which retarded further dissolution of the matrix. Moreover, bound water could adsorb metal ions to form a new protective film, which played an important role in improving the corrosion resistance of the Cr41CoFeNi EHEA. However, the elemental segregation and chemical potential difference between phases increased the defects in the passive film and accelerated its pitting corrosion of low potential phase. Moreover, the (Co, Fe, and Ni)-enriched FCC structured phase was preferentially eroded.