Microstructure and electrochemical performance of plasma sprayed Fe45Mn35Co10Cr10 high-entropy alloy coating in different corrosive solutions

A Fe45Mn35Co10Cr10 high-entropy alloy (HEA) coating was prepared on Ti6Al4V alloy by plasma spraying. The microstructure, chemical elements and phases of obtained coating were analyzed using a field emission scanning electron microscope, energy dispersive spectrometer and X-ray diffraction, respectively. The electrochemical performances in 0.1 M H2SO4, 0.1 M NaOH and 3.5 % NaCl solutions were investigated using an electrochemical workstation, and the corrosion model was also established to reveal the corrosion mechanism. The results show that the Fe45Mn35Co10Cr10 HEA coating is composed of face-centered cubic, FeCr2O4, MnCr2O4 and MnO phases, which forms the mechanical bonding with the substrate. The HEA coating has the lowest corrosion current density icorr, highest polarization resistance Rpo and largest charge transfer resistance Rct in 0.1 M H2SO4 solution, exhibiting the highest electrochemical corrosion resistance. The corrosion mechanism of HEA coating is pitting corrosion in three kinds of corrosive solutions, in which Fe45Mn35Co10Cr10 HEA coating forms the stable corrosion products in 0.1 M H2SO4 solution.