Wang Q Y, Zheng Y F
Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001, China.
Dent Mater. 2008 Sep;24(9):1207-11. doi: 10.1016/j.dental.2008.01.011. Epub 2008 Mar 11.
The aim of this study was to investigate the electrochemical behavior of Ti50Ni47.2Co2.8 alloy in deaerated artificial saliva solutions with binary NiTi alloy as reference and to characterize the composition and structure of the passive film after polarization tests.
The corrosion behavior of NiTiCo alloy was systematically studied by open circuit potential, potentiodynamic and potentiostatic techniques. The surface characterization after anodic polarization tests were demonstrated by XPS. The electrolytes were maintained at 37 degrees C by immersing the test cell in water bath. 500 mV vs. SCE was applied on the samples for potentiostatic tests. The metal ions concentration was measured by ICP/OES.
Potentiodynamic and potentiostatic tests results showed that the corrosion behavior of NiTiCo was similar to that of NiTi alloy. With the increase of pH value of the electrolytes, both corrosion potential (Ecorr) and pitting corrosion potential (Eb) decreased. XPS results revealed that the outmost passive film consisted mainly of TiO2 which were identical with that of NiTi alloy. The Ni ion release amount of NiTiCo was very close to that of NiTi alloy as examined by ICP/OES. Neither Ti nor Co ion was detected due to the detection limitation.
The corresponding relationship between corrosion behavior and pH value of the artificial saliva should be taken into consideration during the application of orthodontic wires. The addition of Co had little effect on the corrosion behavior of NiTi as well as the formation of the passive film.
本研究旨在以二元镍钛合金为参比，研究Ti50Ni47.2Co2.8合金在除气人工唾液溶液中的电化学行为，并对极化测试后的钝化膜组成和结构进行表征。
采用开路电位、动电位和恒电位技术系统研究了NiTiCo合金的腐蚀行为。通过XPS对阳极极化测试后的表面特征进行了表征。通过将测试池浸入水浴中，使电解质保持在37℃。在样品上施加相对于饱和甘汞电极（SCE）为500 mV的电位进行恒电位测试。通过电感耦合等离子体发射光谱仪（ICP/OES）测量金属离子浓度。
动电位和恒电位测试结果表明，NiTiCo的腐蚀行为与NiTi合金相似。随着电解质pH值的增加，腐蚀电位（Ecorr）和点蚀电位（Eb）均降低。XPS结果表明，最外层钝化膜主要由TiO2组成，与NiTi合金的相同。通过ICP/OES检测，NiTiCo的Ni离子释放量与NiTi合金非常接近。由于检测限的原因，未检测到Ti和Co离子。
在正畸丝的应用过程中，应考虑人工唾液腐蚀行为与pH值之间的对应关系。Co的添加对NiTi的腐蚀行为以及钝化膜的形成影响不大。
