Investigating the electrochemistry of organic coated metal surfaces at defect sites

该项目是巴斯夫涂料与斯旺西大学和伦敦帝国理工学院合作的更大合作伙伴关系的一部分，其主题将涉及进一步了解应用于金属表面的保护性有机涂层的腐蚀引起的失效。该项目的主要重点将是对渗透性有机涂层缺陷的有限空间内发生的过程的基本理解，直至底层金属。在这一领域的详细知识是设计改进涂层技术的关键，这些技术可以在引起损伤的情况下提供“自我修复”能力，并且一小块金属区域暴露（例如，油漆车身上的石头碎片）。研究将集中在三个具体的兴趣领域：(i)开发适当的电化学技术和实验方法，以便研究渗透有机涂层效应下暴露金属表面腐蚀行为的动态变化。（ii）缺陷形貌和保护性有机涂层成分，特别是底漆层，对暴露金属表面发生的腐蚀过程和腐蚀动力学的影响。待研究的金属基材将包括冷轧、镀锌和锌铝镁合金涂层钢，而有机涂层将集中在简单的模型涂料系统上。（iii）缺陷处暴露金属的电化学动态变化与保护涂层内储存的缓蚀剂释放的相关性，最初侧重于工业标准的缓蚀剂颜料技术，但扩展到新颖的智能缓蚀剂添加剂。该研究将在斯旺西大学腐蚀研究小组的实验室中通过扫描开尔文探针（SKP），扫描振动电极技术（SVET）以及动电位和电化学阻抗谱方法，使用综合的原位和非原位电化学表征进行。表面化学和结构表征将使用一系列仪器进行，包括x射线光电子能谱（XPS）、掠角x射线衍射（XRD）和场发射枪扫描电子显微镜（fg - sem）。项目任务：-开发实验方法，研究渗透涂层缺陷处暴露的金属基板的电化学，最初集中于应用SKP监测腐蚀电位的变化，应用SVET确定阳极和阴极电流的随时间变化。预计微探针电极技术的使用也可以用于表征外极化缺陷处的金属衬底电化学。-系统研究缺陷尺寸、有机涂层厚度和成分对暴露金属腐蚀行为动态变化的影响。-对缺陷部位的腐蚀后金属表面进行化学表征，以阐明导致腐蚀行为动态变化的现象。

The project forms part of a larger partnership involving BASF Coatings, in collaboration with Swansea University and Imperial College London, where the main theme will involve furthering the understanding of corrosion-induced failure of protective organic coatings when applied to metal surfaces. The principal focus of the project will be directed towards a fundamental understanding of the processes which occur within the confined space of a penetrative organic coating defect, down to the underlying metal. A detailed knowledge in this area is key in designing improved coating technologies which provide "self-healing" capability under situations where damage is induced, and a small area of metal becomes exposed (e.g., a stone chip in painted car bodywork). The research will concentrate on three specific areas of interest: (i) the development of appropriate electrochemical techniques and experimental methodologies which allow the study of dynamic changes in the corrosion behaviour of exposed metal surfaces at a penetrative organic coating effect.(ii) the influence of the defect topography and composition of the protective organic coating, with particular emphasis on the primer layer, on the corrosion processes and kinetics of corrosion occurring on the exposed metal surface. The metal substrates to be studied will comprise cold rolled, galvanized and zinc-aluminium-magnesium alloy coated steel, while organic coatings will concentrate on simple model paint systems.(iii) correlation of dynamic changes in the electrochemistry of the exposed metal at the defect with release of inhibitive agents stored within the protective coating, initially focusing on industry standard corrosion inhibitive pigment technologies, but extending to novel, intelligent release additives.The investigation will be carried out using comprehensive in-situ and ex-situ electrochemical characterization by means of scanning Kelvin Probe (SKP), Scanning Vibrating electrode technique (SVET), alongside potentiodynamic and electrochemical impedance spectroscopy methods in the laboratories of the Swansea University corrosion research group. Surface chemical and structural characterization will be carried using a suite of instrumentation including X-ray-photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (XRD), and field emission gun scanning electron microscopy (FEG-SEM).Project Tasks:- Develop experimental methodologies to investigate the electrochemistry of exposed metal substrates at a penetrative coating defect, initially concentrating on the application of SKP to monitor changes in corrosion potential and SVET to determine time-dependent changes in anodic and cathodic currents. It is anticipated that the use of microprobe electrode technology can also be adapted to characterise metal substrate electrochemistry at a defect under external polarisation.- A systematic study the effect of defect size, organic coating thickness and composition on dynamic changes in the corrosion behaviour of the exposed metal.- Carry out chemical characterisation of the post-corrosion metal surface at the defect site to elucidate the phenomena responsible for the observed dynamic changes in corrosion behaviour.