Investigation of chloride-induced depassivation of iron in alkaline media by reactive force field molecular dynamics
Investigation of chloride-induced depassivation of iron in alkaline media by reactive force field molecular dynamics
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DOI：
10.1038/s41529-019-0081-6
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发表时间：
2019-04-23
影响因子：
5.1
通讯作者：
Isgor, O. Burkan
中科院分区：
文献类型：
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作者：
DorMohammadi, Hossein;Pang, Qin;Isgor, O. Burkan
铁在碱性介质中的钝化性使碳钢能够在混凝土中用作钢筋，这构成了现代基础设施的大部分。然而，氯化物，主要来自除冰化学品或海盐，可以打破铁钝化膜，引起主动腐蚀。尽管最近在铁钝化的纳米表征的进展，显着的差距存在于我们的理解的动态过程，导致氯化物诱导的钝化膜的击穿。在这项研究中，氯离子诱导的去钝化铁在pH 13.5的NaOH溶液中进行了研究，用反应力场分子动力学。去钝化过程由膜表面附近的电解质的局部酸化开始，随后铁溶解到电解质中，并且在钝化膜中形成铁空位。氯化物不渗透的钝化膜，但主要作为一种催化剂，形成铁空位，向金属/氧化物界面扩散，这表明与点缺陷模型一致的去钝化机制。
The passivity of iron in alkaline media enables the use of carbon steel as reinforcement in concrete, which makes up the majority of modern infrastructure. However, chlorides, mainly from deicing chemicals or marine salts, can break down the iron passive film and cause active corrosion. Despite recent advances in nanoscale characterization of iron passivity, significant gaps exist in our understanding of the dynamic processes that lead to the chloride-induced breakdown of passive films. In this study, chloride-induced depassivation of iron in pH 13.5 NaOH solution is studied using reactive force field molecular dynamics. The depassivation process initiates by local acidification of the electrolyte near the film surface, followed by iron dissolution into the electrolyte, and iron vacancy formation in the passive film. Chlorides do not penetrate the passive film, but mainly act as a catalyst for the formation of iron vacancies, which diffuse toward the metal/oxide interface, suggesting a depassivation mechanism consistent with the point-defect model.