Corrosion mechanism of annealed equiatomic AlCoCrFeNi tri-phase high-entropy alloy in 0.5 M H2SO4 aerated aqueous solution

This work investigates the corrosion mechanism of annealed equiatomic AlCoCrFeNi tri-phase alloy in 0.5 M H2SO4 aerated aqueous solution. Experimental results indicate that the B2 matrix is preferentially corroded away while grain-boundary FCC and labyrinth-like BCC endure, consistent with the tendency of formation energy for monolayer hydroxide on the (001) plane of three phases calculated by the first principle based on density function theory. Furthermore, the stable passive current density is related to lower k(sp) values of Co(OH)(3), Fe (OH)(3), and Cr(OH)(3), while the annealing effect on enhancing corrosion resistance is owing to the more uniformity of passive hydroxide film.