镁合金表面低温熔盐扩散铝涂层及其钝化膜的半导体导电行为研究

Low temperature molten salt diffusion aluminum coating on magnesium alloy has been considered as a great potential approach to providing the protection of magnesium alloys. The passive behavior had been observed for the diffusion coatings with continuous intermetallic compound layers.It is generally accepted that a passive behavior is significantly beneficial for improving the corrosion resistance. Unfortunately, a fundamental understanding of the mechanisms for the corrosion failure of the diffusion coatings is lacking. For establishing the mechanism of corrosion failure and quantifying the process of corrosion failure, in this project, we suggest that the forming mechanism of passive behavior is the formation of the continuous passive film. Based on the electrochemical theory, we found that the passive film have the semiconductor characteristics.Three passive behavior parameters of formation potential, potential range of dynamic equilibrium and pitting break potential on the process of the passive film formation and breaking are investigated.On three stage the composition,structure,thickness,film-forming mechanism and semiconductor conductive properties of the passive film are investigated and the semiconducting behavior will change. The relationship of the corrosion resistance on the different stages with the carrier density will be analyzed.The innovative approach for researching the failure mechanism of diffusion coating on the magnesium alloy has been proposed.The theoretical support for quantitative corrosion failure behavior of diffusion coating has been provided. Thorough understanding and quantification of the degradation mechanisms may provide useful guidance in the development of high performance diffusion coatings and be applied to direct the practical use of such coatings.

镁合金表面低温熔盐扩散渗铝是极具发展潜力的表面防护技术，该方法获得的连续金属间化合物层在电解质溶液中呈现出明显的钝化行为，大大提高镁合金的腐蚀性能，而目前对此类涂层腐蚀失效机理的基础研究还相对缺乏。为了确立镁合金低温熔盐扩散铝涂层的腐蚀失效机理和量化腐蚀失效行为，本项目提出涂层钝化行为产生的原因是形成了连续的钝化膜，并且发现其钝化膜具有半导体的导电特性这一创新性的结果。研究钝化膜形成和破坏过程中的形成电位、动态平衡电位区间以及点蚀击破电位对应的三个阶段，及其不同阶段钝化膜的成分、结构、厚度、成膜机制、半导体导电特性以及半导体导电行为的变化规律，同时分析不同阶段涂层耐蚀性能与载流子密度之间的联系。为镁合金熔盐扩散铝涂层的腐蚀失效机理提出创新性的研究思路，为量化扩散层的腐蚀失效行为提供理论支持。透彻理解和量化冶金扩散层的腐蚀失效机理对于提升扩散层的性能及推动扩散层的实际应用具有重要指导意义。

镁合金表面低温熔盐扩散渗铝是极具发展潜力的表面防护技术，该方法获得的连续金属间化合物层在电解质溶液中呈现出明显的钝化行为，大大提高镁合金的腐蚀性能。本项目提出了涂层钝化行为产生的原因是形成了连续的钝化膜，并且发现其钝化膜具有半导体的导电特性这一创新性的结果。研究了钝化膜形成和破坏过程中的形成电位、动态平衡电位区间以及点蚀击破电位对应的三个阶段，及其不同阶段钝化膜的成分、结构、厚度、成膜机制、半导体导电特性以及半导体导电行为的变化规律，同时分析不同阶段涂层耐蚀性能与载流子密度之间的联系，确立了镁合金低温熔盐扩散铝涂层的腐蚀失效机理和量化腐蚀失效行为，为镁合金熔盐扩散铝涂层的腐蚀失效机理提出创新性的研究思路，为量化扩散层的腐蚀失效行为提供理论支持。透彻理解和量化冶金扩散层的腐蚀失效机理对于提升扩散层的性能及推动扩散层的实际应用具有重要指导意义。