A comparative study on the corrosion behavior of porous and dense NiTi shape memory alloys in NaCl solution

The corrosion behaviors of porous and dense NiTi shape memory alloys with the same nominal composition were investigated in a 0.9% aqueous NaCl solution using electrochemical methods. The study clarified the role of the porous structure in influencing the corrosion behavior of the porous NiTi alloys, which exhibited porosity values ranging from 35.5% to 63.8%. The results indicated that the porous NiTi alloy was more susceptible to localized corrosion than was the dense NiTi alloy. However, the porous NiTi alloy sample with a higher porosity did not suffer more serious corrosion than the one with a lower porosity. Furthermore, the potential distribution exists on the pore wall of the porous NiTi alloys as a result of current flow within the pore electrolyte. Thus, the role of potential distribution inside the pore and porous structure in the corrosion behavior of the porous NiTi alloys is an important factor. (C) 2011 Elsevier Ltd. All rights reserved.