npj: 相场模拟—再现复杂的金属材料点腐蚀

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点腐蚀是最具破坏性的腐蚀形式之一，可导致结构的灾难性破坏。暨往的相场计算模型无法同时考虑电解质中的离子传输、阳极和阴极电化学反应，以及复杂的材料微观结构。

来自香港理工大学机械系的石三强教授领导的团队，建立了考虑上述因素的相场模拟，研究了不锈钢浸入温和盐水后的点腐蚀坑的生长。这个模型可用于研究扩散控制，或者界面反应控制的腐蚀过程。作者开发了几种方程式，考虑了多种离子的迁移和浓度因素，引入了一个序参数来描述腐蚀界面的变化。由此构建的模型模拟了从介观到宏观尺度的腐蚀过程，成功地演示了两个腐蚀坑可以聚结形成更宽的腐蚀坑，残余应力的作用，以及腐蚀沿不同晶体取向的发展速率。成功地模拟复杂的腐蚀过程，可以帮助我们更好地理解腐蚀并减少其影响。

该文近期发表于npj Computational Materials 4:38 (2018)。，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Phase-field model of pitting corrosion kinetics in metallic materials 

Talha Qasim Ansari, Zhihua Xiao, Shenyang Hu, Yulan Li, Jing-Li Luo & San-Qiang Shi

Pitting corrosion is one of the most destructive forms of corrosion that can lead to catastrophic failure of structures. This study presents a thermodynamically consistent phase field model for the quantitative prediction of the pitting corrosion kinetics in metallic materials. An order parameter is introduced to represent the local physical state of the metal within a metal-electrolyte system. The free energy of the system is described in terms of its metal ion concentration and the order parameter. Both the ion transport in the electrolyte and the electrochemical reactions at the electrolyte/metal interface are explicitly taken into consideration. The temporal evolution of ion concentration profile and the order parameter field is driven by the reduction in the total free energy of the system and is obtained by numerically solving the governing equations. A calibration study is performed to couple the kinetic interface parameter with the corrosion current density to obtain a direct relationship between overpotential and the kinetic interface parameter. The phase field model is validated against the experimental results, and several examples are presented for applications of the phase-field model to understand the corrosion behavior of closely located pits, stressed material, ceramic particles-reinforced steel, and their crystallographic orientation dependence.

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