严酷海洋大气环境中冷轧板在非稳态薄液膜下的腐蚀行为与机理研究

The nature of the corrosive damage occurred at the surface of cold rolled (CR) steel sheet in severe marine atmosphere is a corrosion electrochemical process occurred under unsteady state thin electrolyte film. Differed from traditional metal/thin electrolyte film system, a multi-interface steel/oil film/thin electrolyte film/ wet atmosphere system can be formed on CR sheets during manufacture and warehousing, which complicates the mass transfer processes of such corrosion medium as O2 and Cl- and their mechanism. Thus, it is necessary to renew the understanding for the corrosion process under unsteady thin electrolyte film involved in the CR sheets. In this project, the relationship among environmental factors, the formation of unsteady state thin electrolyte film and the electrochemical behavior are investigated by using the electrochemical microcapillary technique and scanning Kelvin probe (SKP). The marine atmospheric corrosion principle of the CR sheet can be disclosed and the critical condition for the corrosion occurrence can be determined therein. In addition, a setup for measuring the localized electrochemistry under unsteady state thin electrolyte film is employed, in which the environmental factors can be controlled and coupled. With the aid of the setup, the influence of the oil film on the corrosion behavior of the CR sheets can be clarified and the dynamic law for the diffusion process of corrosion medium can be obtained for the multi-interface system. Furthermore, scanning Kelvin probe force microscopy and Raman spectroscopy will be applied to in-situ monitor the dynamic variation of surface morphology, electrochemical state and corrosion products. Therefore the corrosion damage principle and the mechanism of the CR sheets under unsteady state thin electrolyte film will be established especially for severe marine atmospheric environment.

冷轧板在海洋大气环境中发生表面腐蚀破坏的本质是非稳态薄液膜下的腐蚀电化学过程。有别于传统的金属/薄液膜体系，生产和储运过程中冷轧板表面形成了由冷轧板/油脂/薄液膜/湿大气组成的多界面体系，这使腐蚀介质（O2，Cl-等）的传质过程及作用机制更加复杂，因此需要对非稳态薄液膜下冷轧板腐蚀过程进行重新认识。本项目利用毛细管微电极和SKP研究了环境影响因素、非稳态薄液膜形成和膜下腐蚀电化学行为三者之间的关系，揭示了模拟海洋大气环境中冷轧板表面的腐蚀电化学行为规律，探明引起腐蚀的临界条件。运用多因素耦合非稳态薄液膜微区电化学装置探明油膜对冷轧板腐蚀过程的影响机制，获得腐蚀性介质在多界面体系中发生扩散的动力学规律。将扫描开尔文力显微镜与Raman光谱相结合，对冷轧板表面形貌、表面电化学状态及腐蚀产物成分的变化过程进行原位动态监测，揭示严酷海洋大气环境中冷轧板在非稳态薄液膜下发生腐蚀破坏的规律与机理。

冷轧板在海洋大气环境中发生表面腐蚀破坏的本质是非稳态薄液膜下的腐蚀电化学过程。 有别于传统的金属/薄液膜体系，储运过程中防锈油膜的存在可能会改变冷轧板腐蚀的进程。本项目基于不同冷轧板在室外长期暴露实验与室内短期模拟环境实验中的腐蚀行为，运用宏观电化学手段（极化曲线、交流阻抗等）与微区电化学手段（SKP，SKAFM等）并配合相应的腐蚀产物分析方法（XRD, Raman），揭示了不同环境条件下不同表面状态冷轧板的腐蚀行为规律，同时，也对不同时间尺度下冷轧板表面腐蚀的萌生、发展进行了细致的跟踪和分析并由此推知其腐蚀机制。另外，通过不同钢种腐蚀行为特征的差异性研究，获得了环境影响因素与冷轧板腐蚀敏感性的对应关系，侵蚀性离子浓度与冷轧板腐蚀速度、腐蚀产物之间的作用规律。研究表明，油膜的存在对IF钢腐蚀机理影响不大，但会改变氯离子对DP钢腐蚀电化学过程的作用机制。 不同环境因素中，氯离子的存在是影响冷轧板腐蚀的敏感因素；不同氯离子浓度下，IF钢和DP钢的耐蚀行为差异不同，高氯离子浓度对IF腐蚀的加速作用更大。不同冷轧板表面锈点的萌生和扩展机制差异与其表面微观相（夹杂）的电化学特性密切相关。