金属表面点蚀的稳态过程数值研究

Numerical study on steady pitting process of metal surface

  • 摘要:
      目的  腐蚀会严重影响舰船设备的使用寿命,了解腐蚀机理及对腐蚀进行预测能有效地减缓腐蚀对舰船设备的危害。
      方法  构建了格子Boltzmann腐蚀模型,该模型可描述包含多相多组分流动与扩散、电化学反应和金属点蚀的稳态全过程。应用此模型,研究浸没于液体腐蚀环境中的金属表面单坑点蚀稳态过程;分析腐蚀化学反应速率、腐蚀溶液扩散系数、腐蚀产物扩散系数对腐蚀程度的影响。通过数值模拟,获得金属表面点蚀坑的形貌变化特征。
      结果  结果显示,对于金属表面单坑点蚀的稳态过程,由于钝化膜与金属基体构成了“大阴极,小阳极”的电化学腐蚀体系,使腐蚀稳态点蚀将持续向金属材料基体的纵深发展,并且初生蚀孔除自身发生点蚀外,还将在蚀孔底部产生次生蚀孔。在不同影响因素下,腐蚀程度随腐蚀反应速率和反应物组分扩散系数的增大而增大,而随腐蚀产物扩散系数的增大而减小。
      结论  通过该腐蚀模型,可模拟出与真实金属相近的腐蚀形貌变化特征。

     

    Abstract:
      Objectives  The service life of the shipboard equipment will be seriously affected in the harsh corrosive environment of seawater. Therefore, it can effectively reduce the equipment damages due to corrosion by understanding corrosion mechanism and predicting corrosion.
      Methods  Lattice Boltzmann (LBM) corrosion model can be used to describe multiphase multicomponent flow and transmission, electrochemical reaction and metal steady pitting process. Based on this model, a numerical study is conducted to simulate a single corrosion pit on a metal surface immersed in the liquid corrosive environment; the effects of corrosion reaction rate, corrosion solution diffusion coefficient and corrosion product diffusion coefficient on the degree of corrosion are analyzed.
      Results  Morphological changes of the pit on the metal surface can be obtained by the numerical simulation. The numerical results show that, the pitting corrosion will be deeper because of the electrochemical corrosion system of large cathode and small anode formed by passivation film and metal matrix during the steady corrosion process of the single pit on the metal surface; the primary pitting hole will produce secondary pitting hole at the bottom. A conclusion obtained by changing the factors in the model is that, the degree of corrosion increases as the corrosion reaction rate increases, increases as the diffusion coefficient of the reactant components increases, and decreases as the corrosion product diffusion coefficient increases.
      Conclusions  The similar corrosion morphology of the real metal can be simulated through this corrosion model.

     

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