Microstructure and electrochemical performance of plasma sprayed Cu11.85Al3.2Mn0.1Ti alloy coating in different corrosive solutions

A Cu11.85Al3.2Mn0.1Ti alloy was coated on Ti6Al4V alloy by plasma spraying (PS). The microstructure and phases of obtained coating were analyzed using a super-depth of field microscope (SDFM) and X-ray diffraction (XRD), respectively. The electrochemical performances of Cu11.85Al3.2Mn0.1Ti alloy coating in 3.5% NaCl, 0.1 M NaOH and 0.1 M H2SO4 solutions were evaluated using an electrochemical workstation, which were determined by the potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). The results show that the potential Ecorr of Cu11.85Al3.2Mn0.1Ti alloy coating in 3.5% NaCl, 0.1 M NaOH and 0.1 M H2SO4 solutions is −0.22, −0.16, and −0.13 V, respectively, and the corresponding corrosion current density icorr was 5.96, 24.41 and 13.78 μA·cm–2, respectively. Moreover, the corrosion resistance of Cu11.85Al3.2Mn0.1Ti alloy coating in 0.1 M H2SO4 and 0.1 M NaOH solution is higher than that in 3.5% NaCl solution, in which the corrosion rate is the highest in 3.5% NaCl solution. The corrosive media on the loose coating surface easily penetrate into the alloy coating, and the micropores are formed along the grain boundary of alloy coating, which accelerates its corrosion progress.