Abstract
In recent years, there has been growing interest in the use of TiNi shape memory alloys (SMAs) as functional/smart materials for a variety of applications. In this study, (Ti51Ni49-xRex) shape memory alloy has been modified by adding various amounts of rhenium (Re) (x = 0, 0.1 and 0.3 %) at the expense of Ni. As a first step towards studying the effect of Re (as an alloying element) on the microstructure, phase transformation, mechanical properties and uniform and pitting corrosion processes of the three tested (Ti51Ni49-xRex) shape memory alloys, we have reported the results of cyclic polarization measurements on passivity breakdown and initiation and propagation of pits on the surfaces of the three tested alloys in aerated neutral 0.05 M KBr solution. The potentiodynamic anodic polarization curves of the three tested alloys exhibited no active dissolution region due to spontaneous passivation. The passive region is followed by pitting corrosion as a result of breakdown of the passive film induced by Br- anions. Cyclic polarization measurements allow the pitting potential (E-pit) and the repassivation potential ((Erp)) to be determined. E-pit increased with increase in Re content in the tested samples. Pitting morphology studies showed that the severity of pitting attack suppressed upon alloying Ti51Ni49 shape memory alloy with Re. These findings demonstrated that the presence of Re enhanced the pitting corrosion resistance of the tested alloys to an extent depending on the Re content. ICP-AES (inductively coupled plasma atomic emission spectrometry) was also employed as an independent method of chemical analysis to confirm results obtained from cyclic polarizations measurements.