Electrochemical and microstructural study of Cu–Al–Ni shape memory alloy

The corrosive behaviour of Cu–Al–Ni shape memory alloy in deaerated 0.5 M NaCl solution at 20 °C was studied by means of open circuit potential measurements, linear polarization, potentiodynamic polarization measurements, cyclic voltammetry and electrochemical impedance spectroscopy measurements. The electrode surface was examined by light microscope, SEM, XRD and EDX methods. The polarization measurements have shown that corrosive behaviour of Cu–Al–Ni alloy in NaCl solution was dominated by the Cu component. The results of impedance measurements at open circuit potential have shown that the overall impedance of the system increases with immersion time due to continuous growth of the passive film on the alloy surface. The XRD and EDX analysis showed the presence of copper, aluminium and nickel compounds, Cu-oxides and Cu-chlorides on alloy surface.

► We examine corrosion behaviour of Cu–Al–Ni shape memory alloy.
► Adsorption of chloride ions leads to the decrease of EOCP and the breakdown of the protective surface oxide film.
► Polarization behaviour was determinated by the dissolution of copper to soluble cuprous chloride ion complex (CuCl2−).
► The microstructure consisted of grains with martensite plates.
► After corrosion testing occured of corrosion products at Cu–Al–Ni surface.