镁合金腐蚀与防护关键科学问题的研究

Wide application of magnesium is restricted by its poor corrosion resistance for a long time. At present, there exist three bottleneck problems in the field of corrosion and protection of magnesium: First, development of the corrosion theory lags behind the research on the design and preparation for new type magnesium, which makes it difficult to develop new magnesium with high strength and good corrosion resistance. Second, systematic research is lacking on how to carry out anti-corrosion treatment on magnesium with variable composition，processing technology and pre-treatment. Third, studies on anti-corrosion coatings hardly involve the common problems, causing slow development of technological design theory. Accordingly, this program aims to carry out research on effect of new microstructure and corrosion environment on the corrosion behavior of magnesium so as to clarify the corrosion mechanism based on Mg-Al alloy system and Mg-RE-Zn system, relationship between alloy composition, processing technology, pre-treatment and corrosion resistance of anti-corrosion coating and technological design theory about four new protective coatings including chemical conversion coating based upon the concept of Lewis acidity/pH, self-densification micro-arc oxidation coating, functional coating with excellent electrical conductivity and good corrosion resistance and self-healing metal-organ silicone composite coating used in the middle temperature of ocean environment to provide scientific evidence and theory support on magnesium corrosion and protection.

耐蚀性能差一直是制约镁合金获得广泛应用的关键性问题。目前，镁合金腐蚀与防护领域面临三个瓶颈性的问题：第一，新型镁合金腐蚀理论的研究滞后于合金的设计与制备，难以为开发新型高强耐蚀镁合金提供理论指导；第二，不同成分、加工工艺和前处理状态的镁合金应如何进行防腐蚀处理，尚缺乏系统地研究；第三，防护涂层技术的研究缺乏对共性问题的讨论，工艺设计理论发展滞后。针对于此，本项目以Mg-Al合金、Mg-RE-Zn合金为研究体系，研究新型显微结构和新环境对镁合金腐蚀行为的影响规律，阐明新型镁合金的腐蚀机理；构建合金成分—加工工艺—前处理状态—防护涂层耐蚀性能之间的相关性；研究基于路易斯酸度/pH值概念为基础的化学转化膜、自致密化微弧氧化膜、导电-耐蚀功能性涂层、海洋中温自修复涂层在内的四种新概念防护涂层，并建立相应的工艺设计理论,为解决镁合金的腐蚀与防护问题提供科学依据和理论支撑。

耐蚀性能差一直是制约镁合金获得广泛应用的关键性问题。本项目围绕镁合金腐蚀与防护的关键科学问题：1）研究LPSO、新型析出相对稀土镁合金腐蚀行为的影响机理；2）金属表面状态及显微组织对镁合金防护涂层耐蚀性能的影响；3）新型镁合金防护涂层的设计理论。在研究中原创性地提出了“酸比”理论，把握界面反应“溶解-电离-沉积”过程的主要特征，建立热力学与动力学之间的关联，为开发新型表面处理技术提供了理论基础。借鉴金属凝固若干概念开展交叉学科研究，控制处理液的成分过冷度与临界形核尺寸，解决了转化膜开裂与增厚难以兼顾的传统难题；将“酸比”理论与陶瓷领域学科交叉，通过溶液设计控制沉积物成分，确保弧光放电过程中陶瓷涂层的固液烧结和增韧，解决微弧氧化涂层孔隙率过高的本质性缺点，最终形成了系列性的绿色、高耐蚀镁合金表面处理技术。新技术大量应用于国防建设与国民经济领域。环保型镁合金转化膜技术在航天工业建立生产线，替代了使用50余年的高污染六价铬技术；“耐蚀-功能性”涂层在两个型号的战略导弹上交付使用。研究成果丰富和完善腐蚀电化学的相关理论，为解决镁合金的腐蚀与防护问题提供科学依据和理论支撑。