Corrosion behavior of phosphorus ion-implanted Ni50.6Ti49.4 shape memory alloy

Pretreatment of NiTi alloy by plasma-based phosphorus implantation (PBII) is of interest in order to make beta-particle-emitting radioactive stents. Corrosion properties of PBII-treated and un-treated NiTi alloys have been tested with anodic polarization curves in 1% NaCl solution at 37 °C. PBII treatment can increase the open-circuit corrosion potential (Ecorr) and decrease the corrosion current density (Icorr). The anodic polarization curves of PBII-treated NiTi alloy show a ‘secondary passivation’ phenomenon in the potential range of 0.72 to 1.28 V. The existence of P2O5 can probably be connected with the so-called secondary passivation phenomenon.