The corrosion deterioration of reinforced passivation Film: The impact of defects

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 gamma-FeOOH in passivation film has a strong resistance to corrosion in solution, which corresponds to its high corrosion prevention. The perfect structure of gamma-FeOOH is hard to deteriorate. However, introducing the defects in the passivation film structure can facilitate corrosion deterioration. By introducing the [001] and [100] defects in the gamma-FeOOH structure, the interaction between passivation film and solution is increased. But only the [100] defects can lead to structural deterioration. The difference between the [001] and [100] defects are originated from the competitive effects between the O atoms in gamma-FeOOH and the O atoms in water on Fe atoms. The gamma-FeOOH structure deteriorates when the O atoms in water are winning. Moreover, the nano products of gamma-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.

Automated summary

This study reveals the nano-process of passivation film corrosion using reactive molecular dynamics. The resistance of γ-FeOOH layer structure in passivation film to corrosion is found, and the deterioration of passivation film structure by introducing defects is investigated. The competitive effects between O atoms in γ-FeOOH and O atoms in water on Fe atoms play a critical role in the deterioration process.