In reinforced concrete, the first step of steel corrosion is the structural deterioration of the passivation film that can prevent further corrosion. Due to the nanoscale properties of passivation film structure, understanding its deteriorated mechanism is still a challenge. Here, the nano-process of passivation film corrosion is revealed by employing reactive molecular dynamics. It is found that the layer structure of γ-FeOOH in passivation film has a strong resistance to corrosion in solution, which corresponds to its high corrosion prevention. The perfect structure of γ-FeOOH is hard to deteriorate. However, introducing the defects in the passivation film structure can facilitate corrosion deterioration. By introducing the [0 0 1] and [1 0 0] defects in the γ-FeOOH structure, the interaction between passivation film and solution is increased. But only the [1 0 0] defects can lead to structural deterioration. The difference between the [0 0 1] and [1 0 0] defects are originated from the competitive effects between the O atoms in γ-FeOOH and the O atoms in water on Fe atoms. The γ-FeOOH structure deteriorates when the O atoms in water are winning. Moreover, the nano products of γ-FeOOH deterioration are also observed. This work reveals the fundamental deteriorated process of passivation film and is also the first step to exploring the corrosion of steel bars in the engineering environment.

在钢筋混凝土中，钢腐蚀的第一步是钝化膜的结构恶化，可以防止进一步的腐蚀。由于钝化膜结构的纳米级特性，了解其劣化机制仍然是一个挑战。在这里，通过采用反应分子动力学揭示了钝化膜腐蚀的纳米过程。发现钝化膜中γ-FeOOH的层状结构在溶液中具有很强的抗腐蚀能力，这与其抗腐蚀能力强相对应。γ-FeOOH的完美结构难以劣化。然而，在钝化膜结构中引入缺陷会促进腐蚀恶化。通过引入 [0  0  1] 和 [1  0 0] γ-FeOOH结构缺陷，钝化膜与溶液的相互作用增强。但只有[1  0  0]缺陷会导致结构劣化。[0  0  1]和[1  0  0]缺陷之间的差异源于γ-FeOOH中的O原子与水中的O原子对Fe原子的竞争效应。当水中的 O 原子获胜时，γ-FeOOH 结构会恶化。此外，还观察到了γ-FeOOH劣化的纳米产物。这项工作揭示了钝化膜的基本劣化过程，也是探索钢筋在工程环境中腐蚀的第一步。