目的 针对镁合金涂层破损后快速腐蚀问题,将微胶囊自修复涂层与微弧氧化膜相结合,制备微弧氧化复合自修复涂层,研究其耐腐蚀性能。方法 采用原位聚合法,以尿素-三聚氰胺-甲醛为预聚体,制备包覆桐油的微胶囊,将微胶囊按照质量分数（以环氧树脂的质量为基准）为0%、5%、10%、15%分散在环氧树脂中,分别喷涂在镁合金基体和微弧氧化膜表面,制备微胶囊自修复涂层和微弧氧化复合自修复涂层。通过红外光谱仪和热重分析仪分析微胶囊的化学结构和热稳定性,采用SEM对膜层的表面形貌及修复后的形貌进行分析,通过拉开法测试涂层与基体之间的附着力,通过电化学测试和盐雾试验探讨微胶囊添加量对单一自修复涂层和复合自修复涂层的修复效果,以及对其耐腐蚀性能的影响。结果 涂层划痕区域的修复效果随着微胶囊含量的提升而明显提高,当微胶囊的质量分数超过 10%时涂层的结合力明显下降,最佳的微胶囊质量分数为10%。电化学阻抗解析微弧氧化复合自修复涂层电阻（Rc）为1.12×105 W·cm2,与单一自修复涂层相比提高了3个数量级,与未添加微胶囊的微弧氧化环氧涂层相比,提高了2个数量级,盐雾测试1 000 h后划痕处无明显腐蚀剥落。结论 微弧氧化复合自修复涂层的耐腐蚀性能明显优于单一自修复涂层,冶金结合的微弧氧化膜作为镁合金基体与自修复层之间的中间层,遏制了由镁基体丝状腐蚀扩散所致的有机涂层快速剥离,保障了自修复涂层的结构稳定性,从而减缓了腐蚀扩展速率,有效提升了涂层的自修复效果和耐蚀性。
Abstract
In order to inhibit the rapid corrosion of magnesium alloy coatings after damage, micro-arc oxidation composite self-healing coatings are prepared by combining microcapsule self-healing coatings with micro-arc oxide films to study their corrosion properties. Microcapsules encapsulating tung oil is synthesized via in situ polymerization using a melamine-urea- formaldehyde (MUF) prepolymer. By precisely adjusting the reaction process conditions, microcapsules exhibiting a homogeneous particle size distribution and elevated encapsulation efficiency are successfully synthesized. The as-prepared microcapsules are subsequently incorporated into epoxy resin at varying mass fractions (0%, 2%, 5%, 10%, and 15%) to fabricate self-healing coatings. Concurrently, a ceramic layer with superior corrosion resistance is generated on magnesium alloy substrates through micro-arc oxidation (MAO) treatment. The chemical structure and thermal stability of microcapsules are analyzed by infrared spectroscopy and thermogravimetric analyzer. A Scanning Electron Microscope (SEM) is employed to characterize the morphological features of the microcapsules, the surface topography of the coating, and the morphological changes observed post-repair. On this basis, the distribution of microcapsules in the coating system is deeply analyzed, and the actual effect of microcapsules on coating damage repair is evaluated. Simultaneously, electrochemical testing techniques and salt spray testing methodologies are employed to assess the corrosion resistance of the coating. Furthermore, the influence mechanism of the doping amount of microcapsules on the impedance characteristics of the coating is investigated. A comparative analysis between conventional self-healing coatings and MAO-integrated self-healing coatings is performed to elucidate the reinforcement mechanisms introduced by the MAO layer on the overall coating performance. The repair capacity at scratch sites is progressively improved with increasing microcapsule content. At lower microcapsule loadings, the insufficient release of healing agent during crack propagation hinders complete damage mitigation, resulting in reduced repair efficiency. Upon increasing the microcapsule content to 10%, crack-induced release of healing agent becomes substantially enhanced, enabling polymerization-driven formation of a dense protective layer at the crack interface. This layer effectively blocks corrosive media infiltration. Combined with the coating adhesion test, the degree of adhesion between the coating and the substrate is determined. Electrochemical impedance spectroscopy (EIS) reveals that coatings with 10% microcapsule content exhibits a resistivity of 1.12×105 Ω·cm², marking a two-order-of-magnitude improvement compared with the pristine state, which confirms significantly enhanced corrosion protection. Salt spray testing further validates the long-term durability, as no visible corrosion-induced delamination occurs at scratch sites after 1 000 h exposure. In contrast to conventional self-healing coatings, MAO-integrated self-healing coatings exhibit superior corrosion resistance. The MAO layer functions as a foundational barrier, enhancing the coating's mechanical integrity while significantly mitigating corrosive media penetration toward the substrate. SEM cross-sectional analysis reveals well-defined interfacial bonding between the MAO layer and the self-healing topcoat, further augmenting the system's overall performance. Electrochemical impedance spectroscopy (EIS) data show that the composite coatings display notably higher impedance magnitudes compared with standalone self-healing counterparts, with post-healing values increasing further. These findings underscore a synergistic effect between the MAO layer's barrier properties and the self-healing mechanism, cumulatively elevating the coating's protective efficacy. Electrochemical impedance spectroscopy (EIS) measurements reveal that the MAO-integrated self-healing coatings exhibit a significantly enhanced corrosion resistance compared with bare MAO layers, as evidenced by a substantial increase in low-frequency impedance modulus. Post-healing evaluation further demonstrates that the composite coatings achieve higher impedance values and extend the salt spray resistance duration relative to uncoated magnesium alloy substrates. Notably, the MAO-integrated self-healing systems outperform standalone self-healing coatings in corrosion protection efficacy. The MAO layer effectively suppresses filiform corrosion on the magnesium substrate, significantly retarding corrosion propagation kinetics and thereby extending the coating's operational lifespan.
关键词
镁合金 /
微胶囊 /
微弧氧化 /
自修复 /
复合涂层 /
腐蚀机理
Key words
magnesium alloy /
microcapsule /
micro-arc oxidation /
self-healing /
composite coating /
corrosion mechanism
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基金
广州市重点研发计划（2024B01J0037）; 辽宁省应用基础研究计划(2022JH2/101300007); 魏桥国科高研院-中国科学院金属研究所研发项目（GYY-JSBU-2022-006）; 沈阳市自然科学基金专项（23503605）
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