Controlling Corrosion of Lightweight Magnesium Alloys through Improved Surface Stability

通过提高表面稳定性控制轻质镁合金的腐蚀

• 批准号: RGPIN-2015-05182
• 负责人: Kish, Joseph
• 金额: $ 1.82万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=680400
• 关键词: Controlling; Corrosion; Lightweight; Magnesium; Alloys

Reducing the overall mass of transportation vehicles by the use of lightweight alloys is one of the means by which improved fuel efficiency and reduced harmful emissions can be attained. Wrought magnesium (Mg) alloy components, with their high specific strength and stiffness, provide significant opportunities to achieve these goals. Arguably the key technical issue preventing widespread implementation of Mg alloy components is the high rate of dissolution (corrosion) in aqueous environments. This is driven in large part by the inherent reactivity of Mg (lowest standard reduction potential among industrial engineering metals), the high rate of the hydrogen evolution reaction (cathode activation) that dominates the cathodic process on corroded surfaces and the tendency of the native protective oxide surface film to breakdown and be replaced with a relatively thick partially-protective corrosion product film. This proposal serves to to elucidate and control the film-based cathode activation that drives the localized corrosion upon Mg surfaces. Specific short-term goals include: (i) identify the controlling film composition and/or structure factors responsible for the cathode activation by synthesizing and studying surrogate filmed Mg surfaces, (ii) resolve the evolution of the air-formed oxide film on corroding Mg surfaces in-situ using laser Raman spectroscopy (LRS) to validate the film composition findings of the ex-situ transmission electron microscopy (TEM) method, and (iii) control (reduce) cathode activation by ion implanting H2 evolution poisons within the film of pre-oxidized Mg surfaces as an initial step towards developing an enabling surface modification corrosion control technology. Conventional electrochemical polarization techniques will be employed to characterize the global electrochemical response of corroding Mg surfaces in aqueous chloride solutions and to accelerate breakdown processes under controlled current (galvanostatic polarization) conditions. The scanning vibrating probe technique will be used to resolve and track the anodic and cathodic processes as they move across freely corroding and anodically polarized magnesium surfaces. High resolution electron microscopy techniques will be used to study ex-situ the site-specific film structure and chemistry involved in initiating and sustaining the cathode activation in time. The ex-situ examinations rely on the premise that the films will not be significantly altered upon removal from solution. This issue will be specifically addressed by conducting a comparative in-situ characterization of the composition of the surface films formed using laser Raman spectroscopy. The is critical to illuminate pathways for new discovery opportunities for the design and development of improved corrosion-resistant pre-treatment coating processes for structural wrought Mg alloys. **

通过使用轻质合金来减少运输车辆的总质量是提高燃油效率和减少有害排放的手段之一。锻造镁（Mg）合金部件具有高的比强度和刚度，为实现这些目标提供了重要的机会。可以说，阻止镁合金部件广泛应用的关键技术问题是在水环境中的高溶解速率（腐蚀）。这在很大程度上是由Mg的固有反应性（工业工程金属中最低的标准还原电位）、在腐蚀表面上主导阴极过程的析氢反应（阴极活化）的高速率以及天然保护性氧化物表面膜破裂并被相对厚的部分保护性腐蚀产物膜替代的趋势驱动的。该建议用于阐明和控制驱动Mg表面上的局部腐蚀的基于膜的阴极活化。具体的短期目标包括：（i）通过合成和研究替代成膜Mg表面来识别负责阴极活化的控制膜组成和/或结构因素，（ii）使用激光拉曼光谱（LRS）原位解析腐蚀Mg表面上的空气形成的氧化物膜的演变，以验证非原位透射电子显微镜（TEM）方法的膜组成发现，和（iii）通过在预氧化的Mg表面的膜内离子注入H2析出毒物来控制（减少）阴极活化，作为开发能够实现的表面改性腐蚀控制技术的初始步骤。传统的电化学极化技术将被用来表征腐蚀镁表面在氯化物水溶液中的整体电化学响应，并在受控电流（恒电流极化）条件下加速击穿过程。扫描振动探针技术将被用来解决和跟踪阳极和阴极过程，因为他们跨越自由腐蚀和阳极极化镁表面移动。高分辨率电子显微镜技术将用于研究非原位的特定位点的膜结构和化学参与启动和维持阴极激活的时间。非原位检查依赖于膜在从溶液中移除时不会显著改变的前提。这个问题将具体解决进行比较原位表征的组成形成的表面膜，使用激光拉曼光谱。这是至关重要的，以照亮新的发现机会的设计和开发的结构变形镁合金的耐腐蚀预处理涂层工艺的途径。 **