Department of Biomedical and Chemical Engineering, Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York.
J Biomed Mater Res B Appl Biomater. 2011 Aug;98(2):369-78. doi: 10.1002/jbm.b.31861. Epub 2011 Jun 6.
Hard coatings for articulating surfaces of total joint replacements may improve the overall wear resistance. However, any coating approach must take account of changes in corrosion behavior. This preliminary assessment analyzes the corrosion kinetics, impedance and mechanical-electrochemical stability of 100 μm thick plasma sprayed chromium oxide (Cr₂O₃) coatings on bearing surfaces in comparison to the native alloy oxide films on Co-Cr-Mo and Ti-6Al-6V. Cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and mechanical abrasion under potentiostatic conditions were performed on coated and substrate surfaces in physiological saline. SEM analysis characterized the coating morphology. The results showed that the corrosion current density values of chromium oxide coatings (0.4-1.2 μA/cm²) were of the same order of magnitude as Ti-6Al-4V alloy. Mechanical abrasion did not increase corrosion rates of chromium oxide coatings but did for uncoated Co-Cr-Mo and Ti-6Al-4V. The impedance response of chromium oxide coatings was very different than Co-Cr-Mo and Ti-6Al-4V native oxides characterized by a defected coating model. More of a frequency-independent purely resistive response was seen in mid-frequency range for the coatings (CPE(coat) : 40-280 nF/cm² (rad/s)(1-α) , α: 0.67-0.83) whereas a more capacitive character is seen for Co-Cr-Mo and Ti-6Al-4V (CPE(ox) around 20 μF/cm² (rad/s)(1-α) , α around 0.9). Pores, interparticle gaps and incomplete fusion typical for thermal spray coatings were present in these oxides which could have influenced corrosion resistance. The coating microstructure could have allowed some fluid penetration. Overall, these coatings appear to have suitable corrosion properties for wear surfaces.
用于关节置换的活动表面的硬涂层可以提高整体耐磨性。然而，任何涂层方法都必须考虑到腐蚀行为的变化。本初步评估分析了 100μm 厚的等离子喷涂氧化铬（Cr₂O₃）涂层在承载表面上的腐蚀动力学、阻抗和机械电化学稳定性，与 Co-Cr-Mo 和 Ti-6Al-6V 的本征合金氧化膜进行了比较。在生理盐水中，对涂层和基底表面进行了循环动电位极化、电化学阻抗谱和恒电位下的机械磨损。SEM 分析表征了涂层形貌。结果表明，氧化铬涂层的腐蚀电流密度值（0.4-1.2μA/cm²）与 Ti-6Al-4V 合金处于同一数量级。机械磨损不会增加氧化铬涂层的腐蚀速率，但会增加未涂层的 Co-Cr-Mo 和 Ti-6Al-4V 的腐蚀速率。氧化铬涂层的阻抗响应与 Co-Cr-Mo 和 Ti-6Al-4V 的本征氧化物非常不同，其特征是存在有缺陷的涂层模型。涂层在中频范围内呈现出更多的与频率无关的纯电阻响应（CPE(coat)：40-280 nF/cm²（rad/s）（1-α），α：0.67-0.83），而 Co-Cr-Mo 和 Ti-6Al-4V 则呈现出更具电容性的特征（CPE(ox)约为 20μF/cm²（rad/s）（1-α），α约为 0.9）。这些氧化物中存在典型的热喷涂涂层的孔隙、颗粒间间隙和不完全融合，这可能影响了耐腐蚀性。涂层的微观结构可能允许一些流体渗透。总的来说，这些涂层似乎具有适合磨损表面的腐蚀性能。
