Fundamental interfacial chemical processes, structures, and compositions underlying corrosion reactions

腐蚀反应的基本界面化学过程、结构和成分

• 批准号: RGPIN-2018-06672
• 负责人: Noël, James
• 金额: $ 2.48万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714386
• 关键词: Fundamental; interfacial; chemical; processes; structures

Many of the metals that we use to construct such diverse items as nuclear reactors, coins, aircraft, orthopaedic implants, and pop cans are so unstable that, without the protection of a 3-5 nanometres-thick layer of oxide (a “passive film”), they would quickly react with their surroundings and revert to the chemical forms in which they existed before we mined and refined them. This project uses advanced surface analysis and electrochemical techniques capable of probing such thin layers to investigate how passive films form on titanium, zirconium, and nickel-based superalloys, their physical structure, their composition (which varies from metal to metal), and how they degrade or react with their surroundings. The goals are to learn how to form passive oxide films that resist degradation and how to make passive films that repair themselves if they become damaged. Another significant challenge for metals is localized corrosion, in which the damage, rather than being distributed across the metal surface, is focused in a small area, resulting in deep penetration. An insidious form of localized corrosion is crevice corrosion, which occurs largely unseen in cracks and hidden areas in joints and under coatings where the narrow geometry restricts movement of chemical species into or out of the crevice. A build-up of corrosive chemical species occurs within the crevice, leading to accelerated attack. This project develops innovative electrochemical methods to analyze and map the distribution of corrosive species and resultant corrosion damage inside crevices, which we will relate to the geometry of the crevice and the composition of the materials from which it is formed. We will also use X-ray imaging to “see” the internal structure inside a crevice as it corrodes. The knowledge gained will be used to help understand, avoid, and mitigate the effects of crevice corrosion and to design more resistant alloys. Finally, we will explore the role of hydrogen in corrosion reactions. Hydrogen is abundant in corrosion, as it is produced by the reaction of a metal with water or acid, but difficult to detect in or on metal surfaces without destroying the metal being analyzed. We will use beams of neutrons or electrons to determine concentration of hydrogen on metal surfaces during or following corrosion reactions to investigate the possibility that surface hydrogen is responsible for two curious phenomena in corrosion called the “negative difference effect” (which accelerates corrosion of magnesium alloys) and “cathodic modification” (which protects titanium alloys from corrosion). We will also measure amounts of hydrogen-driven corrosion occurring hidden within crevices, unaccounted for in damage predictions based only on oxygen-driven corrosion occurring outside the crevice. Preliminary measurements on titanium and nickel-based alloys suggest that hydrogen reactions multiply corrosion damage by 60-500% or more.

我们用来制造核反应堆、硬币、飞机、矫形植入物和易拉罐等各种物品的许多金属都非常不稳定，如果没有3-5纳米厚的氧化物层（一种“钝化膜”）的保护，它们会迅速与周围环境发生反应，并恢复到我们开采和精炼它们之前存在的化学形式。 该项目使用先进的表面分析和电化学技术，能够探测这种薄层，以研究钛，锆和镍基高温合金上的钝化膜如何形成，它们的物理结构，它们的成分（因金属而异），以及它们如何降解或与周围环境反应。目标是学习如何形成抗降解的钝化氧化膜，以及如何制造在受损时能够自我修复的钝化膜。 金属面临的另一个重大挑战是局部腐蚀，其中损伤不是分布在金属表面，而是集中在一个小区域，导致深度渗透。局部腐蚀的一种潜在形式是缝隙腐蚀，它主要发生在裂缝和接缝中的隐藏区域以及涂层下，其中狭窄的几何形状限制了化学物质进出缝隙的运动。在裂缝内会产生腐蚀性化学物质的积聚，导致加速侵蚀。 该项目开发了创新的电化学方法来分析和绘制裂缝内腐蚀性物质的分布和由此产生的腐蚀损伤，我们将与裂缝的几何形状和形成裂缝的材料成分相关。我们还将使用X射线成像来“看到”裂缝内部的内部结构，因为它腐蚀。所获得的知识将用于帮助理解，避免和减轻缝隙腐蚀的影响，并设计更耐腐蚀的合金。 最后，我们将探索氢在腐蚀反应中的作用。氢在腐蚀中是丰富的，因为它是由金属与水或酸反应产生的，但很难在不破坏被分析金属的情况下在金属表面或金属表面上检测到。我们将使用中子或电子束来确定腐蚀反应期间或之后金属表面上的氢浓度，以研究表面氢对腐蚀中两种奇怪现象的可能性，称为“负差异效应”（加速镁合金的腐蚀）和“阴极改性”（保护钛合金免受腐蚀）。我们还将测量隐藏在裂缝内的氢驱动腐蚀量，这些腐蚀量在仅基于裂缝外发生的氧驱动腐蚀的损坏预测中未被考虑。对钛和镍基合金的初步测量表明，氢反应使腐蚀损坏增加60-500%或更多。