Electropolishing of NiTi for Improving Biocompatibility

A modified electrolyte （CH 3 COOH-HClO 4 -A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy.Using the proposed parameters,a homogeneous and uniform surface was obtained.Atomic force microscopy （AFM） revealed that the surface roughness （Ra） for EP sample （23.21 nm） was close to mechanical polishing （MP） sample （19.36 nm）.Analysis by X-ray photoelectron spectroscopy （XPS） showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample.Measurements using potentiodynamic polarization in Hanks’ solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV （vs SCE）,while the MP sample was broken down at 650 mV.The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.