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Corrosion and microstructural analysis of CuAlNi shape memory alloy in 0.9 % NaCl solution before and after heat treatment

The electrochemical behavior in 0.9 % NaCl solution (pH = 7.4) at 37°C of a CuAlNi shape memory alloy (SMA) before and after heat treatment at two different temperatures were studied by means of open circuit potential (EOC) measurements, linear and potentiodynamic polarizations and also OM and SEM-EDX microanalysis. The investigations were performed on samples in as-cast state and two different heat treated states (at temperatures of 850 °C/60’/WQ (K1) and 920 °C/60’/WQ (K2)). Higher polarization resistance and lower corrosion current density of heat treated CuAlNi alloy (K1 and K2) compared to CuAlNi alloy in as-cast state indicate beneficial influence of heat treatment on corrosion resistance of CuAlNi alloy. Scanning electron microscopy investigations revealed deposits of corrosion products on the surface in the form of spikes. The EDS analysis have showed that the surface contains the significant amount of oxygen and chloride compounds. Optical micoscropy shows that after removing the surface layers of corrosion products, damages due to pitting corrosion were clearly visible on electrode surface.

corrosion ; CuAlNi SMA ; polarization ; microstructure

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