Design of next-generation automotive corrosion protective coatings by improving inhibitor transport properties

保护性涂料行业目前正面临数十亿磅挑战，以找到成功的材料替代有毒的六价铬基防腐蚀剂，通常作为微溶盐颜料掺入有机涂层中。欧盟已指定2019年为铬（VI）使用的“日落”日期，之后将被禁止。因此，迫切需要确定新的环境腐蚀抑制技术，即使没有更好的保护能力，也具有同等的保护能力。该项目提供了一个与世界领先的汽车涂料公司巴斯夫汽车公司合作的绝佳机会，以开发新的无Cr（VI）腐蚀抑制技术，从而更有效地提供腐蚀保护。涉及基于磷酸盐的技术的现有技术仍然是有限的，因为活性腐蚀抑制剂释放到涂层缺陷区域中没有得到很好的控制。因此，现在对开发智能释放颜料的性质有很大的兴趣，其中腐蚀抑制物质被储存并且仅在侵蚀性腐蚀诱导剂存在下“按需”释放。此外，还需要改善抑制剂物质从涂层本体到需要它们的区域（例如暴露下层金属的缺陷）的输送。目前，只有有限量的来自紧邻缺陷的涂层的抑制剂可用于保护暴露的金属。通过在涂层内引入长程渗流网络，希望增强缓蚀剂向缺陷区域的传输，可以在暴露的金属处产生更有效的腐蚀抑制。项目目标：1.研究使用现有技术的磷酸盐基颜料和含有各种腐蚀抑制物质的新型智能释放离子交换颜料对渗透性涂层缺陷的抑制效率.对上述颜料的不同涂层内载量进行详细研究，以评估对抑制剂释放速度的影响。评估新型抑制剂输送系统，如纳米管储库、离子交换树脂和矿物质，导电聚合物网络作为在保护性有机涂层内引入长距离渗透颜料网络的手段。4.为了评估来自优化系统的抑制剂的长距离传输如何影响涂层失效的机理，涂层失效是由于渗透缺陷附近腐蚀驱动的阳极和/或阴极剥离引起的脱粘。这项工作的主要目标是为技术上重要的轻合金表面开发下一代保护涂层，通常是铝和可能的镁汽车合金牌号，尽管最佳性能的技术也可应用于钢的保护。该工作计划将利用世界领先的先进电化学扫描技术的专业知识，结合高通量方法来量化腐蚀防护效率，并提供对缓蚀机制的机械理解。调查将通过扫描开尔文探针（SKP），扫描振动电极技术（SVET），以及斯旺西大学腐蚀研究小组实验室中的动电位和电化学阻抗谱方法。表面化学和结构表征将使用世界一流的仪器套件进行，包括X射线光电子能谱（XPS），掠射角X射线衍射（XRD）和场发射枪扫描电子显微镜（FEG-SEM），可在材料研究中心在工程学院。

The protective coatings industry is currently facing a multi-billion pound challenge to find successful materials substitution for toxic hexavalent chromium-based anti-corrosion agents, typically incorporated as sparingly soluble salt pigments within an organic coating. Cr(VI) use has been assigned a "sunset" date of 2019 by the European union, after which it will be banned. As such there is an urgent need to identify new, environmentally corrosion inhibitive technologies showing equivalent, if not better protective capability. This project provides an excellent opportunity to work with a world leading company involved in the automotive coatings market, namely BASF Automotive, to develop new Cr(vi)-free corrosion inhibitive technologies which will deliver corrosion protection more effectively. The current state of the art, involving phosphate based technology, remains limited since release of active corrosion inhibitive agents into coating defect regions is not well controlled. As a result, there is now significant interest in exploiting the properties of intelligent-release pigments, in which corrosion inhibitive species are stored and only released "on-demand" in the presence of aggressive corrosion-inducing agents. Furthermore, there is also a need to improve the transport of inhibitor species from the bulk of the coating to the areas where they are required (e.g. defects where the underlying metal is exposed). Currently, only a finite quantity of inhibitor originating from the coating in the immediate vicinity of the defect may available to protect exposed metal. By introducing long-range percolation networks within the coating, it is hoped that enhanced transport of inhibitor to defect regions can produce significantly more effective corrosion inhibition at the exposed metal.Project aims:1. To investigate the efficiency of inhibition at penetrative coating defects using current state of the art phosphate based pigments and novel smart-release ion-exchange pigments containing various corrosion inhibitive species.2. To carry out detailed studies with varying in-coating loadings of the above mentioned pigments to evaluate the effect on speed of inhibitor release.3. To assess novel inhibitor delivery systems such as nanotube reservoirs, ion exchange resins and minerals, conducting polymer networks as a means of introducing a long-range percolation pigment network within the protective organic coating.4. To evaluate how long range transport of inhibitor from an optimised system influences the mechanism of coating failure due to de-adhesion originating from corrosion-driven anodic and/or cathodic disbondment in the vicinity of a penetrative defect.The main thrust of the work will be to develop next-generation protective coatings for technologically important light alloy surfaces, typically aluminium and possibly magnesium automotive alloy grades, although the best performing technologies may also be applied to the protection of steel. The program of work will exploit world-leading expertise in advanced electrochemical scanning techniques, coupled with high throughput methodologies to quantify corrosion protection efficiency and provide mechanistic understanding of inhibition mechanisms.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 world class suite of instrumentation including X-ray-photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (XRD), and field emission gun scanning electron microscopy (FEG-SEM), available in the Materials Research Centre at the College of Engineering.