An investigation of the corrosion behaviour of a FeNiCoAITa shape memory alloy in 3.5 wt-% NaCl solution

In this study, the corrosion behaviour of an FeNiCoAlTa (NCAT) shape memory alloy in 3.5% (ww(-1)) NaCl solution was evaluated. Linear polarisation resistance and potentiodynamic polarisation tests were conducted at 25 degrees C. An open circuit potential (OCP) of -381mV (vs. saturated calomel reference electrode) and a corrosion rate (CR) of 0.0174 mmy(-1) were obtained. The NCAT alloy did not show any passivation in the 3.5% (ww(-1)) NaCl solution. Its corrosion behaviour was very similar to that of G10180 (AISI 1018) carbon steel with the NCAT showing a lower CR and a less active OCP. Its corrosion in the solution was a combination of general dissolution and localised attack (pitting). Aging heat treatment caused beta-Ni3Al phase, and tantalum to precipitate on the grain boundaries, resulting in chemical species segregation between the grain boundaries and the grains. The chemical segregation caused intergranular corrosion of the alloy.