Trépanier C, Tabrizian M, Yahia L H, Bilodeau L, Piron D L
GRBB, Biomedical Engineering Institute, Ecole Polytechnique de Montréal, Quebec, Canada.
J Biomed Mater Res. 1998 Winter;43(4):433-40. doi: 10.1002/(sici)1097-4636(199824)43:4<433::aid-jbm11>3.0.co;2-#.
Because of its good radiopacity, superelasticity, and shape memory properties, nickel-titanium (NiTi) is a potential material for fabrication of stents because these properties can facilitate their implantation and precise positioning. However, in vitro studies of NiTi alloys report the dependence of alloy biocompatibility and corrosion behavior on surface conditions. Surface oxidation seems to be very promising for improving the corrosion resistance and biocompatibility of NiTi. In this work, we studied the effect on corrosion resistance and surface characteristics of electropolishing, heat treatment, and nitric acid passivation of NiTi stents. Characterization techniques such as potentiodynamic polarization tests, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to relate corrosion behavior to surface characteristics and surface treatments. Results show that all of these surface treatments improve the corrosion resistance of the alloy. This improvement is attributed to the plastically deformed native oxide layer removal and replacement by a newly grown, more uniform one. The uniformity of the oxide layer, rather than its thickness and composition, seems to be the predominant factor to explain the corrosion resistance improvement.
由于镍钛合金（NiTi）具有良好的射线不透性、超弹性和形状记忆特性，它是制造支架的一种潜在材料，因为这些特性有助于其植入和精确放置。然而，关于NiTi合金的体外研究报告了合金生物相容性和腐蚀行为对表面条件的依赖性。表面氧化似乎在改善NiTi的耐腐蚀性和生物相容性方面非常有前景。在这项工作中，我们研究了电抛光、热处理和硝酸钝化对NiTi支架耐腐蚀性和表面特性的影响。使用动电位极化测试、扫描电子显微镜、俄歇电子能谱和X射线光电子能谱等表征技术将腐蚀行为与表面特性及表面处理联系起来。结果表明，所有这些表面处理都提高了合金的耐腐蚀性。这种改善归因于去除了塑性变形的原生氧化层，并被新生长的、更均匀的氧化层所取代。氧化层的均匀性，而非其厚度和成分，似乎是解释耐腐蚀性提高的主要因素。
