Layer formation mechanisms during plasma-anodising of magnesium in dependence of the electrolyte composition

镁等离子阳极氧化过程中的层形成机制与电解质成分的关系

• 批准号: 258050305
• 负责人: Professor Dr.-Ing. Thomas Lampke
• 金额: --
• 依托单位: Professur Werkstoff- und Oberflächentechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/258050305?language=en
• 关键词: Layer; formation; mechanisms; during; plasma; Layer; formation; mechanisms; during; plasma

The potential field of application of magnesium materials is far greater than the application range covered today facilitating a further reduction of energy consumption in mobile systems. However, its poor corrosion and wear resistance is a drawback to many applications, which can be overcome by surface modification. Plasma electrolytic anodic oxidation (PAO) allows for the formation of ceramic oxide coatings on the magnesium substrate improving the corrosion resistance even though a post-treatment (e.g. sealing) is mostly required. There is a lack of knowledge with regard to the interactions of the electrolyte and the magnesium substrate during the PAO process precluding the development of wear resistant coatings or corrosion resistant coatings, which do not require a post-treatment. The interactions between electrolyte, magnesium substrate and formed oxide layers are insufficiently established at the present state of research especially regarding the effect of single electrolyte components and different combinations of them. Thus, electrolytes for PAO are solely designed on an empirical basis and success is highly dependent on the experience of the experimenter. Electrolytes used for PAO of magnesium almost exclusively contain electrolyte components in low concentrations (< 50 g/l). This is perceived as unfavourable by the applicants of the present project because magnesium oxide, which has unfavourable characteristics like low hardness, strength and chemical resistance, is mainly produced during PAO in low-concentrated aqueous solutions. Further, the dissolution of substrate and coating material in the aqueous electrolyte under high polarisation is competing against the coating formation. Preliminary tests showed a strong passivation of the magnesium substrate and the formed oxide layer in high concentrated electrolytes (> 100 g/l of a single component). Thus, the voltage rise in the first seconds of the process is promoted and a wider range of electrical process parameters becomes accessible. Further, both literature and preliminary test results indicate the favourable formation of non-magnesium-oxides or spinels, which leads to better coating characteristics. The proposed research project aims to investigate the passivation and dissolution behaviour of magnesium substrate in the solutions of single electrolyte components and different combinations of them. Using polarisation and electrochemical impedance techniques, the interactions between electrolyte and substrate are systematically analysed and the understanding of the influence on coating growth mechanisms (substrate passivation, discharge evolution, dissolution) is raised. The gained knowledge allows for the composition of electrolytes for a PAO process that aims at attaining defined coating characteristics.

镁材料的应用潜在领域远大于当今所涵盖的应用范围，促进了移动系统中能源消耗的进一步降低。但是，其耐腐蚀和耐磨性不足是许多应用的缺点，可以通过表面修饰克服。血浆电解性阳极氧化（PAO）允许在镁基质上形成陶瓷氧化物涂层，即使需要进行后处理（例如密封），从而提高了耐腐蚀性。在PAO工艺过程中，缺乏关于电解质和镁底物的相互作用的知识，从而排除了耐磨性涂层或耐腐蚀涂层的发展，这不需要后处理。电解质，镁基质和形成的氧化物层之间的相互作用在目前的研究状态不足，尤其是在单个电解质成分及其不同组合的影响方面。因此，PAO的电解质仅根据经验设计，成功高度取决于实验者的经验。用于镁的PAO的电解质几乎完全包含低浓度（<50 g/L）的电解质成分。本项目的申请人认为这是不利的，因为氧化镁具有低硬度，强度和耐化学性（例如低浓缩的水溶液）期间PAO期间产生的氧化镁。此外，在高极化下，底物和涂料材料的溶解正在与涂层形成竞争。初步测试表明，镁底物和高浓度电解质中形成的氧化物层（> 100 g/l单个成分）的强烈钝化。因此，促进了该过程的第一秒内的电压升高，并且可以访问更广泛的电气过程参数。此外，文献和初步测试结果都表明非氧化物或尖晶石的有利形成，这会导致更好的涂层特征。拟议的研究项目旨在研究单个电解质成分的溶液中镁底物的钝化和溶解行为以及它们的不同组合。使用极化和电化学阻抗技术，系统分析了电解质与底物之间的相互作用，并理解对涂层生长机制的影响（底物钝化，放电进化，溶解）的理解。获得的知识允许将电解质组成用于PAO过程，旨在获得定义的涂层特征。