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.

铁在碱性介质中的钝化性能使得可以将碳钢用作混凝土的补强材料，这构成了现代基础设施的大部分。但是，主要来自除冰剂或海盐的氯化物会破坏铁钝化膜并引起主动腐蚀。尽管最近在铁钝性的纳米级表征方面取得了进展，但在我们对导致氯化物引起的钝化膜击穿的动力学过程的理解中，仍然存在巨大的空白。在这项研究中，使用反作用力场分子动力学研究了pH值13.5 NaOH溶液中氯化物诱导的铁的钝化。钝化过程通过在膜表面附近的电解质局部酸化开始，然后将铁溶解到电解质中，并在钝化膜中形成铁空位。