激光电子散斑干涉技术监测奥氏体不锈钢在NaCl溶液中的点蚀敏感性

用动电位极化和电化学阻抗等方法检测1Cr18Ni9Ti、304和316三种奥氏体不锈钢在3.5%NaCl溶液中的点蚀敏感性；用恒电位下的计时电流法结合激光电子散斑干涉技术（ESPI）实时监测这三种材料在3.5%NaCl溶液中阳极极化过程的表面动态变化及点蚀感应时间(τ)。结果表明，当电极表面发生点蚀时，激光电子散斑干涉图上会出现由点蚀产物扩散引起的亮斑。1Cr18Ni9Ti和 304不锈钢的τ值分别是1 s和9 s，316不锈钢的τ值大于50 s。由此可以判断1Cr18Ni9Ti的点蚀敏感性最大，304居中，316的点蚀敏感性最小。此结果与动电位极化和电化学阻抗等电化学方法得出的结果一致。激光电子散斑干涉技术可以做为一种实验室方法监测金属早期点蚀敏感性。

MONITORING THE PITTING SUSCEPTIBILITY OF AUSTENITIC STAINLESS STEEL IN NaCl SOLUTION BY ELECTRONIC SPECKLE PATTERN INTERFEROMETRY

The pitting susceptibility of 1Cr18Ni9Ti、304 and 316 austenitic stainless steel in 3.5 %NaCl solution was monitored by potential dynamic polarization and electrochemical impedance spectroscope. The pitting induction time (τ) and in-situ changes of electrode surface for the three types of materials in 3.5 %NaCl solution were monitered by electronic speckle pattern interferometry (ESPI) and the chrono amperometry. The results indicated that, bright speckles in ESPI images show pitting corrosion occurring on metal surface. The speckles in ESPI were caused by the pitting corrosion products. The value of pitting induction time (τ) for 1Cr18Ni9Ti and 304 steel were 1 s and 9 s. The value of pitting induction time (τ) for 316 steel was more than 50 s. The results of ESPI showed that, in the 3.5 %NaCl solution, the pitting susceptibility of 1Cr18Ni9Ti was the worst of the three types of materials, and the 316 steel was the best. The result of ESPI was in agreement with that of potential dynamic polarization and electrochemical impedance spectroscope. ESPI can be used as a laboratory technique to monitor the initial pitting susceptibility of metals.