不同质量分数氯离子对铬合金钝化膜性能的影响

Influence of different NaCI concentration on passive behavior of Cr alloy in vitro

目的在不同质量分数氯化钠溶液中研究3种铬合金表面钝化膜的性能改变，分析其抗腐蚀性能，以期为铬合金的临床应用提供参考。方法分别配制氯化钠质量分数为1％、2％、3％的人工唾液，分别以钴铬合金、镍铬合金和含钛镍铬合金（各5个）为工作电极，施加0．1V钝化电位600s形成钝化膜。分析3种铬合金的电压-电容关系曲线和时间-电流对数曲线，分析不同氯离子质量分数对3种铬合金表面钝化膜的半导体特性及致密性的影响。结果3种铬合金钝化膜均呈n型半导体特性；随着氯化钠质量分数的增大，3种铬合金钝化膜的载流子密度均增大，当氯化钠质量分数为3％时镍铬合金、钴铬合金和含钛镍铬合金的载流子密度分别增至3．71×10^8、2．34×10^9和7．66×10^9／cm^2，时间一电流对数曲线斜率随之减小，钝化膜稳定性和致密性降低。结论在高氯离子环境中3种铬合金的抗腐蚀性能均降低，严重影响修复体的使用寿命。

Objective To investigate the properties of passive film of three Cr alloys and to analyze their corrosion resistance in the artificial saliva with different NaCl mass fraction in vitro. Methods Artificial saliva with 1% , 2% and 3% NaCl mass fraction was prepared. Cobalt-chromium alloy, nickelchromium alloy and Ti-Ni-Cr alloy were employed as the working electrode in the artificial saliva. Semiconductor properties of passive film on Cr alloy was analyzed by Mott-Schottky plots. In addition, the factors which affect the semi-conductive compact characteristic of the passive film was also discussed. Results The passive film exhibits n-type semi-conductive characters. With the increasing of NaCl mass fraction, the carrier density of the Cr alloys also increased. The carrier density of the cobalt-chromium alloy, nickelchromium alloy and Ti-Ni-Cr alloy are 3.71 ×10^8 , 2. 34 ×10^9, and 7.66 ×10^9/cm^3 respectively. This decreases its donor density and its film stability. Conclusions When exposed to saliva environment with high concentration of chlorine ion, corrosion resistance of the three types of Cr alloys decrease. This will reduce the service life of Cr alloy prosthesis.