Corrosion behavior of Cu−Al−Mn−Zn−Zr shape memory alloy in NaCl solution

Abstract

Abstract The corrosion behavior of a copper-based shape memory alloy (Cu−Al−Mn−Zn−Zr) in 3.5 wt.% NaCl solution was investigated by means of potentiodynamic polarization measurements, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). At the beginning of corrosion, oxidation products formed on the surface of the shape memory alloy and constantly covered the reaction surface, resulting in the decrease of corrosion rate. After 4 d of immersion in NaCl solution, the corrosion product layer became thick and porous, leading to the increase of corrosion rate, and the corrosion reaction mechanism changed from polarization control to diffusion control. The diffusion impedance increased with increasing thickness of the oxide layer for the samples immersed in NaCl solution for 6−15 d. During the whole corrosion process, the reaction mechanism of the alloy changed and the corrosion resistance was improved continuously. The corrosion products mainly contained CuO, ZnO, Al2O3, MnO/Mn2O3, MnO2 and Al(OH)3. Transition of the corrosion products from Cu2O to CuO and Al2O3 to Al(OH)3 occurred during corrosion.