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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g. corrosion) of a confined metal surface
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In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g. corrosion) of a confined metal surface

机译：局限金属表面的电化学溶解（例如腐蚀）的原位纳米到显微成像和生长机理

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摘要

Reactivity in confinement is central to a wide range of applications and systems, yet it is notoriously difficult to probe reactions in confined spaces in real time. Using a modified electrochemical surface forces apparatus (EC-SFA) on confined metallic surfaces, we observe in situ nano- to microscale dissolution and pit formation (qualitatively similar to previous observation on nonmetallic surfaces, e.g., silica) in well-defined geometries in environments relevant to corrosion processes. We follow “crevice corrosion” processes in real time in different pH-neutral NaCl solutions and applied surface potentials of nickel (vs. Ag|AgCl electrode in solution) for the mica–nickel confined interface of total area ∼0.03 mm2. The initial corrosion proceeds as self-catalyzed pitting, visualized by the sudden appearance of circular pits with uniform diameters of 6–7 μm and depth ∼2–3 nm. At concentrations above 10 mM NaCl, pitting is initiated at the outer rim of the confined zone, while below 10 mM NaCl, pitting is initiated inside the confined zone. We compare statistical analysis of growth kinetics and shape evolution of individual nanoscale deep pits with estimates from macroscopic experiments to study initial pit growth and propagation. Our data and experimental techniques reveal a mechanism that suggests initial corrosion results in formation of an aggressive interfacial electrolyte that rapidly accelerates pitting, similar to crack initiation and propagation within the confined area. These results support a general mechanism for nanoscale material degradation and dissolution (e.g., crevice corrosion) of polycrystalline nonnoble metals, alloys, and inorganic materials within confined interfaces.
机译：封闭中的反应性是广泛应用和系统的核心，但众所周知，实时探测封闭空间中的反应非常困难。在受限的金属表面上使用改进的电化学表面力装置（EC-SFA），我们在环境中定义明确的几何结构中原位观察了纳米到微米级的溶解和凹坑形成（与以前在非金属表面（例如二氧化硅）上的观察结果相似）与腐蚀过程有关。我们在不同的pH中性NaCl溶液中实时跟踪“缝隙腐蚀”过程，并对总面积〜0.03 mm 2的云母-镍密闭界面施加镍（相对于溶液中的Ag | AgCl电极）的表面电势。最初的腐蚀以自催化的点蚀进行，通过突然出现直径为6–7μm，深度约为2-3 nm的圆形点蚀可见。在高于10 mM NaCl的浓度下，在封闭区域的外缘开始点蚀，而在低于10 mM NaCl的情况下，在封闭区域内开始点蚀。我们将宏观纳米深坑的生长动力学和形状演变的统计分析与宏观实验的估计值进行比较，以研究初始坑的生长和传播。我们的数据和实验技术揭示了一种机制，该机制表明初始腐蚀会导致形成侵蚀性界面电解质，该界面电解质会迅速加速点蚀，类似于裂纹在有限区域内的萌生和扩展。这些结果支持了限制界面内多晶非贵金属，合金和无机材料的纳米级材料降解和溶解（例如，缝隙腐蚀）的一般机理。

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