铝合金微弧氧化智能自修复涂层研究

Currently, it is an increasing interesting to improve the corrosion protection of plasma electrolytic oxidation (PEO) coating by endowing with self-repairing technology. The existing methods of PEO self-repairing coating can be divided into in-situ doping and post-treatment. However, it is difficult to eliminate the structure defects caused by spark discharge inside the coating for in-situ doping method. As for post-treatment method, it not only endows the coating self-repairing but also improves the compactness of the coating. However, the sealing agent of this kind of coating can’t realize the function of controllable corrosion inhibition and provide long-term prevention. In view of this, metal-organic frameworks (MOF) which can decompose and release corrosion inhibitor under the action of acid was elected to sealing agent, and preparation of PEO intelligent self-repairing coating by regulating the growth of MOF on PEO coating. The main factors affecting the growth of seed layer are clarified, and the design theory of MOF seed layer is established. The correlation of MOF membrane growth with seed layer and MOF solution system was constructed, and the design theory of PEO/MOF self-repairing coating was established. The correlation of corrosion inhibition efficiency with the composition structure of MOF and the decomposition rate of MOF was constructed, and revealing the self-repair mechanism of PEO/MOF coating. Trying to answer the following scientific question: How to regulate the growth of MOF on PEO coating to obtain the PEO coating with high-performance intelligent self-repairing.

通过自修复技术提高微弧氧化（PEO）涂层的防护作用是近些年研究的热点。现有的PEO自修复涂层分为原位掺杂和后处理两大类。原位掺杂法无法消除由于火花放电在涂层内部形成的结构缺陷。后处理法虽然使涂层具备自修复功能的同时又提高了涂层的致密性。但这类涂层的封闭剂无法实现可控缓蚀的作用，难以起到长效防腐蚀的目的。针对于此，本项目拟选用金属有机骨架（MOF）材料，利用其在酸性作用下可分解释放缓蚀剂这一特点，通过调控MOF在PEO涂层的生长，制备PEO智能自修复涂层。阐明影响晶种层生长的主要因素，建立MOF晶种层的设计理论；构建MOF膜生长与晶种层和MOF溶液体系的相关性，建立PEO/MOF自修复涂层设计理论；构建“MOF组成—MOF分解速度—缓蚀效率”的相关性，揭示PEO/MOF涂层自修复机制。最终回答这样一个科学问题：如何调控MOF在PEO涂层上的生长，获得高性能的PEO智能自修复涂层。

随着我国“21世纪海上丝绸之路经济带” 战略的不断推动，海洋工程装备的地位日益凸显，迫切需要开发适用于海洋环境的防腐涂层以推动海洋工程装备产业的发展。本项目融合了微弧氧化(PEO)涂层和自修复技术的各自优势。选用含缓蚀成分的金属有机骨架（MOF）材料对微弧氧化涂层的结构缺陷进行修复，以期获得综合性能优异的PEO自修复涂层。首先采用原位生长法研究MOF材料在铝合金及铝合金微弧氧化涂层表面的生长，结果表明，MOF材料难以连续生长，其原因在于基材与MOF材料的异构性，MOF晶种难以在基材表面生长。然后采用多巴胺对基材表面改性及预制水滑石（LDH）薄膜，研究其对MOF膜层生长影响，结果表明，多巴胺改性对MOF生长影响较小，通过预制LDH可获得连续的MOF膜层，这是由于LDH提供了MOF膜层生长所需的二价金属源。采用二次生长法即在铝合金及PEO膜先生长一层MOF晶种层可为MOF膜层的二次生长提供锚点，有利于MOF膜层生长。同时在晶种液中添加硅烷可以有效提高晶种层的稳定性和耐蚀性，但由于硅烷组分在MOF膜二次生长过程中可能存在水解和降解的作用，影响了晶种层的结构稳定性并影响MOF的进一步生长。研究表明铝合金PEO涂层表面状态，MOF合成工艺，晶种液组成均对MOF的生长产生影响。通过二次生长法以及预制LDH膜层能够有效改善MOF在PEO涂层表明的生长，获得了综合性能优异的PEO/MOF复合膜层。此外，本项目还研究了MOF微纳米颗粒原位掺杂于微电解液中可以降低微弧氧化的放电强度，并在微弧氧化过程中对结构缺陷进行原位修复，显著提高微弧氧化涂层的致密性和耐蚀性能。