小孔腐蚀诱发过程的研究

用电化学方法研究了奥氏体不锈钢在含氯离子和硫酸盐的介质中孔蚀诱发的临界条件和诱发动力学过程,得出临界电位与氯离子浓度、温度和铝元素含量之间的定量关系。孔蚀诱发速度遵循着下式: 1/τ=Aexp/(Ea/RT)[Cl~-]~α[SO~_4~(2-)]~β电子探针分析结果表明,氯离子在膜表面上局部浓集。 根据实验结果,提出了孔蚀诱发的临界核模型。该模型可以解释(1)临界条件的存在和本质,(2)氯离子对钝化膜的局部破坏作用,(3)小孔的再钝化和再钝化小孔的临界尺寸,(4)孔蚀诱发的敏感位置,(5)缓蚀性阴离子的作用,(6)诱导期的含义。

AN IN VESTIGATION OF PITTING INITIATION PROCESS

The critical conditions and the kinetics of pitting initiation in austenitic stainless steels in chloride solutions have been studied by the method of electrochemistry.The relationship between the critical potential and the concentraion of chloride ion,temperature as well as the content of molybdneum is obtained. The rate of pitting initiation follows she equation: Ⅰ/t=Aexp (-Ea/RT) [C1~-]~α [SO_4~(-2)]~β.It is shown by Electron Microprobe analysis that the chloride ions locally concentrate on the film.A critical nucleus model for pitting initiation has been put forward, by whieh the following could be explained: (1)the existance and nature of critical conditions, (2)localized attack of chloride ions on passive film, (3)the repassivating of pits and the critical size of repassivated pits,(4) the sites susceptible to pitting initiation, (5)the effect of inhibiting anions and (6)the physical meaning of induction period.