光照辐射对纯铜海洋大气腐蚀过程的影响机制研究

Light illumination is one of the most important factors affecting the marine atmospheric corrosion process of metal. The specific influencing mechanism is very complicated, and many scientific problems are still unclear. There are many impact factors which affect the generation and separation of the photoinduced electrons and holes, the migration of the charge carriers in the corrosion product layer, and the participation of the photogenerated electrons and holes in the corrosion electrochemical reactions. These impact factors include the semiconductor rectifier characteristics, energy band structure, light response wavelength range, and quantum yield of the corrosion products with semiconductor properties, construction of heterojunction systems, fabrication and formation of the electron transfer channels, photoconductive effect, the corrosion potential of the metal and the redox potential of the electrolyte layer, etc. Related investigations should be carried out to clarify these questions. In the present project, the role of light illumination on the marine atmospheric corrosion process of pure copper will be studied using the test methods from corrosion science, materials science, electrochemistry and photoelectrochemistry. The main aim of this project is to study the mechanism of the effect of light illumination on the marine atmospheric corrosion of pure copper. The studies of this project will reveal the effect of light illumination on the marine atmospheric corrosion rates of pure copper, the effect of light illumination on the initiation, formation and development of the atmospheric corrosion products, and the effect of light illumination on the photoelectrochemical properties of the atmospheric corrosion products formed on the surface of pure copper. Meanwhile, the generation, separation and migration processes of the photoinduced electrons and holes in the atmospheric corrosion products formed on the surface of pure copper will be clarified. The mechanism of the participation of the photogenerated electrons and holes in the corrosion electrochemical reactions of pure copper will be elucidated. The photoelectrochemical theory of marine atmospheric corrosion will be further developed and improved. This project will also provide new ideas and test methods for investigating the marine atmospheric corrosion of pure copper.

光照辐射是影响金属海洋大气腐蚀过程的一个重要因素，具体影响机制很复杂，还有很多科学问题没有弄清楚。例如：腐蚀产物的半导体整流特性、能带结构、光响应波段、量子产率、异质结体系的构筑、电子迁移通道的构建与形成、光电导效应、金属自腐蚀电位和电解液层的氧化还原电位等会如何影响光生电子与空穴的产生、分离、在腐蚀产物中的迁移和参与大气腐蚀电化学反应过程？这些都有待开展相关的研究来弄清楚。本项目以纯铜为研究对象，采用腐蚀科学、材料科学、电化学以及光电化学的测试手段，研究光照辐射对纯铜海洋大气腐蚀过程的影响机理。揭示光照辐射对纯铜海洋大气腐蚀速度、腐蚀产物的生成与发展、腐蚀产物的光电化学效应的影响规律。阐明光生电子空穴在纯铜表面生成的腐蚀产物中的产生、分离、在腐蚀产物中的迁移以及参与纯铜大气腐蚀电化学反应的机理。进一步发展和完善海洋大气腐蚀的光电化学理论。本项目将为纯铜海洋大气腐蚀研究提供新的思路与方法。

基于南海海洋大气腐蚀异常严重的原因分析，开展了本项目的研究。我们研究了光照辐射对纯铜在模拟海洋大气环境下腐蚀过程的影响规律与机制，研究了光照辐射与温度对纯铜海洋大气腐蚀过程的协同作用规律，系统研究了腐蚀产物的光电化学效应，同时，针对金属铜海洋大气腐蚀的绿色防护方法-光电化学阴极保护技术进行了系列探索，研究了它们的光电化学阴极保护性能及光电化学性能的提升机制。本项目研究揭示了光照辐射对纯铜海洋大气腐蚀过程的影响机理，发展和完善了海洋大气腐蚀的光电化学理论。研究发现：光照辐射显著影响并加速了铜的大气腐蚀过程。光照辐射是通过具有半导体性质腐蚀产物的光电化学效应来影响铜大气腐蚀过程的。具有半导体性质的腐蚀产物在受到紫外辐射后会产生光生电子与光生空穴，光生空穴会直接夺取铜阳极溶解产生的电子，加速铜大气腐蚀反应的阳极过程。而光生电子则会转移到与电解液接触的界面并加速氧的还原，从而加速腐蚀反应的阴极过程。光致电流，而非光致电位，是具有半导体性质腐蚀产物光电化学效应的关键判据。我们首次发现，温度是和光照辐射一样重要的影响铜海洋大气腐蚀速度的环境因子。这一结果表明：南海海洋大气腐蚀异常严重的原因除了温度高以外，南海海域高的太阳年辐射总量是一个重要、但又往往被腐蚀科学家们忽视的影响因子。高的温度和太阳辐射总量导致金属材料在南海海洋大气环境下遭受严重的大气腐蚀，这一研究结论为今后南海海洋大气腐蚀的研究指明了方向。本项目开发和改进了多种表征手段，包括发展了铜表面关键腐蚀产物氧化亚铜含量的测定方法，优化了铜表面腐蚀产物的清除方法，将多种分析测试手段引入到腐蚀产物光电化学效应的研究中，首次采用扫描开尔文探针技术表征腐蚀产物的光生电子逸出能力，首次采用光致电流电位特征曲线研究腐蚀产物的半导体类型，首次采用极化曲线减法和交流阻抗技术来研究产物的光电化学效应，极大地丰富了金属大气腐蚀过程的光电化学研究体系。