Corrosion behavior of NiTi shape memory alloy in different simulated body fluids

The corrosion behavior of NiTi alloys in 0.9%NaCl solution, Hank's simulated body solution and Tyrode's simulated blood solution in terms of Ni and Ti ions release has been investigated. The results show that the amount of Ni release increases with the reducing of pH value due to the rise of Flade potentials of nickel, and is highest in Tyrode's simulated blood solution due to being lower oxidation-reduction potential of solution. In 0.9% NaCl solutions containing different Cl^- ions, the higher Cl^- ion concentration corresponds to the higher Ni ion release from NiTi alloys, while the amount of Ti ion release is almost constant and slight. The corrosive behavior of NiTi alloy in physiological environments containing Cl^- ion is Ni selective corrosion, and is pitting corrosion.