The electrochemical behavior and surface analysis of Ti49.6Ni45.1Cu5Cr0.3 alloy for orthodontic usage

The aim of this study was to investigate the electrochemical behavior of Ti49.6Ni45.1Cu5Cr0.3 (TiNiCuCr) alloy in artificial saliva solutions with a wide rage of pH values and to characterize the surface passive film after polarization tests. This article represents the ideal, static environment and associated electrochemical response and comparison values. The corrosion behavior of TiNiCuCr alloy was systematically studied by open circuit potential, potentiodynamic, potentiostatic, and electrochemical impedance techniques. Potentiodynamic and potentiostatic test results showed that the corrosion behavior of TiNiCuCr was similar to that of NiTi alloy. Both corrosion potential (E-corr) and pitting corrosion potential (E-b) showed a pH-dependent tendency that E-corr and E-b decreased with the increase of the pH value. X-ray photoellectron spectroscopy results revealed the composition of the passive film consisted mainly of TiO2 with a little amount of Ni oxides (NiO/Ni2O3) that was identical with NiTi alloy. Besides Ni, a Cu enriched sub-layer was also found. The nickel ion release rate showed a typical time-related decrease as examined by ICP/OES. In conclusion, the addition of Cu and Cr had little effect on the corrosion behavior of NiTi or on the composition and the structure of the passive film. (c) 2007 Wiley Periodicals, Inc.Engineering, BiomedicalMaterials Science, BiomaterialsSCI(E)1ARTICLE2335-34086