轻合金表面构筑智能复合防腐涂层及其自修复工作机理研究

Aiming at the challenge for corrosion of light alloys, this project proposes the construction of intelligent composite anticorrosion coating based on the supramolecular assembly for protection of light alloys. In the project, the feedback active chemical conversion coating will be fabricated to replace non-environmental chromate conversion coating. The mechanized silica nanoparticles equipped with supramolecular nanovalves will be used as the preparation template for “guest” smart nanocontainers, and uniformly distributed in “host” sol-gel coating. They can sensitively respond to the multiple environmental “weak stimuli” around corrosive micro-regions, and rapidly give a feedback of releasing corrosion inhibitor to stop corrosion spread. The advantage of wide response range and high sensitivity will dramatically enhance working efficiency. Secondly, hard/soft microphase-separated hydrogen-bonded supramolecular polymer is put forward and will be constructed simultaneously in the project. The hard segments will provide the mechanical strength needed by primer coating. The dynamic and reversible properties of hydrogen bond implanted in the soft segments as well as the flexibility of polymer chains will facilitate primer coating to accomplish intrinsic self-healing functions after being damaged by external injury. It is expected that the well-designed intelligent composite anticorrosion coating (feedback active chemical conversion coating/supramolecular polymeric primer coating) can self-diagnose and self-repair the possible internal damage within the composite anticorrosion coating, prolong the service life and provide the reliable protection for light alloys.

针对轻合金面临的腐蚀挑战，本项目提出基于超分子组装在其表面构建智能复合防腐涂层的设想。项目计划制备刺激反馈型化学转化膜层取代非环保铬化学转化膜层：以装载超分子纳米阀门的机械化二氧化硅纳米颗粒为模板组建“客体”智能纳米容器，将其掺入“主体”溶胶凝胶涂层中，它能灵敏响应轻合金腐蚀微区内多重环境“微刺激”，并迅速做出反馈—释放缓蚀剂阻止腐蚀扩散。其响应范围广、灵敏度高的优点将大大提升工作效率。项目同时提出构筑硬相/软相微相分离结构的氢键型超分子聚合物为底漆涂层的构想：利用硬相提供底漆涂层所需的机械强度；而将氢键单元植入软相中，利用高分子链的柔顺性以及氢键的可逆性和动态性帮助涂层材料在遭受外部损伤后，实现自主本征自修复功能。寄希望项目设计的智能复合防腐涂层(刺激反馈化学转化膜层/超分子聚合物底漆涂层)能够自动诊断和自发修补复合防腐涂层内部可能出现的损伤，延长服役年限，为轻合金提供更可靠的保护。

针对轻合金面临的腐蚀挑战，本项目基于超分子组装技术在其表面构建智能复合防腐涂层。项目制备的复合防腐涂层体系包括：基于智能纳米容器构筑的刺激反馈型化学转化膜层以及具有硬相/软相微相分离结构的氢键型超分子聚合物底漆涂层。在刺激反馈化学转化膜层研究中，首先提出了无机/有机缓蚀剂协同智能防腐的新概念。项目基于超分子纳米阀门设计了具有氧化还原刺激响应特性的智能纳米容器，利用Ce4+的氧化性可以开启智能纳米阀门，释放纳米容器中装载的有机缓蚀剂。同时，Ce4+被还原为Ce3+，为腐蚀微区提供了无机缓蚀剂Ce3+。无机、有机缓蚀剂的协同作用提高了化学转化膜层局部破损区域的自修复能力，修复后的涂层在0.5M NaCl溶液中浸泡20天后仍无腐蚀电流出现，证明了自修复过程的可靠性和长效性。此外，项目还设计了酸/碱/腐蚀电位三重刺激响应智能纳米容器，腐蚀电位刺激响应功能大幅增强了智能纳米容器在腐蚀微区的响应灵敏度，克服了普通酸/碱双刺激响应智能纳米容器反馈迟缓的弱点。扫描振动电极技术证明微区腐蚀电流在2小时内可以被完全抑制，缩短了五分之四，这有利于在裸露金属表面形成致密的分子膜层。在构建自修复超分子聚合物底漆涂层研究领域内，首先提出了g-C3N4/本征自修复聚氨酯复合材料作为轻合金表面防腐底漆涂层的设计构想。实验证明，g-C3N4的添入在没有影响修复功能的同时，不仅可以使得聚氨酯涂层增强增韧，并且其作为阻隔型填料可以延缓腐蚀介质的渗透。项目原位观察到了涂层的破损修复，闭合腐蚀介质的渗透通道。另外，项目针对自修复防腐底漆涂层存在机械强度和室温自修复效率之间的矛盾，提出了利用“动态硬相”的设计策略制备透明室温自修复涂层材料，使其兼具高机械强度、优异的韧性和快速室温自修复能力。该种材料非常适合作为铝合金表面吸能缓震材料使用。扫描开尔文探针实验证明：一旦受外力强冲击产生微裂纹，涂层可以在室温条件下自发愈合，导致腐蚀电位可以迅速提升进入钝化区，恢复涂层的防腐/防护性能。