Improvement of corrosion resistance and biocompatibility of medical nickel–titanium alloys through forming TiO₂ thin film

Abstract

Nickel-titanium alloys have been investigated for applications to various surgical procedures. However, little is known about the toxicity of Ni-elements and the actual conditions of surface modification of Ni-Ti alloy for preventing the toxicity of Ni. In this study, the corrosion resistance of Ni-Ti alloys was improved through producing a thin TiO 2 film by conducting in-air oxidation and reactive sputtering. These thin films were characterized using field emission type scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. Using the polarization curves obtained by electro-chemical measurements in quasi-living body environment, the corrosion resistance of Ni-Ti super elastic alloy was evaluated. In addition, the effect of an air-oxidized Ni-Ti alloy specimen upon cell multiplication and morphological change of cell were investigated by culturing cells for 72 hrs on a Ni-Ti alloy specimen surface with TiO2 thin film. From these considerations, some trials for establishing a method for TiO 2 thin film formation on the surface of Ni-Ti alloy were conducted from the view point of improving biocompatibility.

Effect of Electrolytic Polishing on Corrosion Fatigue Strength of TiNi Shape Memory Alloy

“…Although the electric potential of the HT material slightly increases in the current density region of 1 × 10 −4 to 1 × 10 −3 mA/cm 2 , the passive regions of the HT-P and HT-EP materials are clearly observed in these curves because of the passive TiO 2 layers on the surface. It is known that a TiO 2 film on the surface of a TiNi SMA increases corrosion resistance, (14) and the results agree with this tendency. Additionally, in general, for the same material, the corrosion resistance is higher with a higher surface roughness.…”