载波钝化可以提高钝化膜稳定性，载波幅值通常覆盖过钝化区，过钝化机制成为载波钝化理论的重要组成部分。过钝化通常被认为是腐蚀破坏过程。然而特定条件下，过钝化处理后金属表现为较钝化处理更为优异的抗腐蚀性能，过钝化有可能成为一种有效的防腐蚀处理方法。从中引申出来的科学问题即是膜的稳定性与膜的微观结构之间的内在联系。在原子尺度下解析钝化膜及膜/基体界面的结构和应力分布特征在过钝化过程中的演变是理解过钝化机制的关键，解析过钝化膜及界面结构和应力分布在氯离子作用下的演变是理解膜稳定性与微观结构关系的关键。本项目拟以球差校正电子显微技术为主要手段，以奥氏体单晶合金为研究对象，在原子尺度下表征过钝化膜及界面的结构、成份及应力分布特征，以其在原子尺度下对过钝化机制加以新的理解，阐明膜的稳定性与微观结构之间的内在联系。项目的完成将大大推进对过钝化机制的认识及理解，对于材料的腐蚀防护具有十分重要的意义。

Alternating voltage (AV) passivation can improve the corrosion resistance of stainless steels. The potential amplitudes of AV usually overlap the transpassive potential region. Clarifying the electrode reaction process involved in the transpassivation is key to deeper understand the AV passivation theory and further optimize the AV parameters. Transpassivation is usually described to be a corrosion damage process, whereas, at some specified conditions, makes metal more corrosion resistant than passivation. Transpassivation, interestingly, is highly implied as a potential means to resisting corrosion. The extracted scientific issue is the intrinsic link between the stability and microstructure of the surface films. Analysing the evolution of the structure and strain state of the passive film as well as the film/metal interface imparted by transpassivation is essential for clarifying the precise transpassivation mechanism. Alongside, resolving the evolution of the structure and strain state of the transpassive film as well as the film/metal interface imparted by chloride ions is key to establish the link between the film stability and its microstructure. In the present project, using aberration-corrected transmission electron microscopy (Cs-corrected TEM) and the fastest and most precise super X-ray energy-dispersive spectrometer (super-XEDS) analysis with four detectors, we would track the evolution of passive films under transpassivation as well as the evolution of transpassive films in chloride-containing media. A new understanding on the mechanism of transpassivation would be proposed based on our observations. The link between the stability and microstructure of the surface films would be established. Accomplishing the present project would promote the understanding on the transpassivation, which is significant for the corrosion protection of materials.