Raman spectroscopic studies of the corrosion of model iron electrodes in sodium chloride solution
Raman spectroscopic studies of the corrosion of model iron electrodes in sodium chloride solution
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DOI：
10.1002/jrs.1810
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发表时间：
2007-12
影响因子：
2.5
通讯作者：
Damien Larroumet;D. Greenfield;R. Akid;J. Yarwood
中科院分区：
文献类型：
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作者：
Damien Larroumet;D. Greenfield;R. Akid;J. Yarwood
在一定的外加电压范围(20~200 mV)和时间范围(0~5h)下，我们研究了单电极和双电极在3.5%的氯化钠溶液中(常温)的非增强拉曼光谱。在这些条件下，我们观察到了最初的“绿色铁锈”(羟基氯化物和/或羟基碳酸盐)的形成，然后是磁铁矿(Fe3O4)的形成，然后是α-FeOOH和伽马-FeOOH的混合物(分别是针铁矿和锂镁铁矿)。这些数据与腐蚀模型一致，在该模型中，最初形成的磁铁矿要么被FeOOH氧化产物层覆盖，要么被取代。对时间和电势的数据拟合表明，虽然产物范围与电势无关，但磁铁矿的形成和随后转化为伽马-FeOOH的相对动力学是电势和时间相关的。通过对干燥腐蚀表面的测绘分析，发现了多种物种，包括绿锈、一些Fe(OH)(3)，以及伽马-FeOOH，可能还有一些β-FeOOH。但没有发现表面磁铁矿，这表明这种物质要么被掩盖了，要么转化为FeOOH。在这项工作中，我们注意到了几个复杂的问题，包括共振效应的干扰(对拉曼强度)和腐蚀过程的不均一性(因此腐蚀表面上的物种分布)。然而，我们认为，非增强拉曼方法的使用导致了更有可能与“真正的”腐蚀过程相关的结论。版权所有(C)2007 John Wiley&Sons，Ltd.
We have explored the un-enhanced Raman spectra of both single and twin electrodes in 3.5% NaCl solution (at ambient temperatures) over a range of applied potentials (between 20 and 200 mV) and times (between 0 and 5 h). Under these conditions, we observed the initial formation of 'green rust' (hydroxychlorides and/or hydroxycarbonates), followed by the formation of magnetite (Fe3O4) and then a mixture of the alpha- and gamma-FeOOH (goethite and lepidocrocite, respectively). These data are consistent with a model for corrosion during which the initially formed magnetite is either covered, or replaced, by layers of the FeOOH oxidation products. Fitting of the data as a function of time and potential shows that, although the product range is independent of potential, the relative kinetics of formation of magnetite and its subsequent conversion to the gamma-FeOOH were potential and time dependent. Analysis by mapping of the dry corroded surface showed a variety of species, including green rust, some Fe(OH)(3), as well as the gamma-FeOOH, and possibly some beta-FeOOH. But no surface magnetite was found, indicating that this material had been either covered up or converted to FeOOH. We noted several complications during this work, including the interference of resonance effects (on the Raman intensities) and the heterogeneity of the corrosion process (and hence distribution of species on the corroded surface). However, we believe that the use of un-enhanced Raman methods has led to conclusions more likely to be relevant to 'real' corrosion processes. Copyright (c) 2007 John Wiley & Sons, Ltd.