用随机分析方法研究磁场对纯镁点蚀过程的影响机理

通过恒电位的方法测量了在有无磁场条件下纯镁的电流-时间响应曲线，并用随机的方法对结果进行分析，研究了磁场对纯镁点蚀产生过程和点蚀成长概率的影响。磁场通过洛仑兹力产生磁流体动力学效应（Magnetohydrodynamic），显著地增加了纯Mg的点蚀敏感性：对于点蚀的产生过程，磁场的存在改变了纯镁的点蚀产生机制。在无磁场作用的条件下，纯镁的点蚀产生过程都遵循“生死异地”的B1机制；在有磁场作用的条件下，纯镁的点蚀产生过程都遵循“相同点蚀并联”的A3机制。磁场不仅增大了点蚀产生速度，而且降低了点蚀的再钝化速度。对于点蚀的成长过程，磁场提高了稳态点蚀的成长概率，更容易成长为较大的点蚀坑。

STOCHASTIC ANALYSIS OF THE MAGNETIC FIELD INFLUENCE ON THE PITTING MECHANISM OF PURE MAGNESIUM

Stochastic analysis was applied to the investigation of the influence of the presence of the magnetic field on the pitting mechanism of pure magnesium, in which pitting corrosion was simulated as the combination of two physical processes: pit initiation and pit growth. The result revealed that the magnetic field could strongly affect the ions in the electrolyte by the magnetohydrodynamics (MHD) phenomena. For the pit initiation process, the mechanism of pit initiation was changed by the presence of magnetic field from the parallel birth and death stochastic model (B1) to the parallel birth stochastic model (A3). The pit generation rate $lambda$ was increased while the repassivation rateμ was decreased, which indicated that magnetic field accelerated the pit initiation process of pure magnesium. For the pit growth process, the stable pit growth mechanism was not changed, but the ability of repassivation of pit corrosion was decreased resulting in a great probability for the stable pit corrosion to grow up with a higher growth rate and finally develop into larger pit cavity.