A mixed-conduction model for oxide films on Fe, Cr and Fe-Cr alloys in high-temperature aqueous electrolytes -: I.: Comparison of the electrochemical behaviour at room temperature and at 200°C
A mixed-conduction model for oxide films on Fe, Cr and Fe-Cr alloys in high-temperature aqueous electrolytes -: I.: Comparison of the electrochemical behaviour at room temperature and at 200°C
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DOI：
10.1016/s0010-938x(02)00008-2
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发表时间：
2002-09-01
影响因子：
8.3
通讯作者：
Sirkiä, P
中科院分区：
文献类型：
--
作者：
Beverskog, B;Bojinov, M;Sirkiä, P
这两部分工作的目的是为铁合金在高温水环境中的腐蚀机制提出一个模型。在本论文的第一部分，对纯Fe、纯Cr、Fe-12% Cr合金和Fe-25%Cr合金在200℃氧化膜形成初期的电化学行为与室温下的实验结果进行了比较。采用伏安法、电化学阻抗谱（EIS）、接触电阻（CER）和接触电阻抗（CEI）等技术得到了实验结果。当温度从室温升高到200℃时，所有材料的无源区电流都会增大。CER、EIS和CEI结果表明，在较高的温度下，薄膜尤其是Fe表面的薄膜明显变厚。此外，EIS和CEI结果给出了200℃下离子输运过程的信息，这在室温下的EIS响应中是没有观察到的。薄膜的电学和输运特性对电势的依赖性表明，200℃下的薄膜也可以用最近引入的室温混合导电模型（MCM）来描述。然而，必须强调在较高的温度下离子缺陷输运的更快速率。本文第二部分详细讨论了MCM对高温氧化膜的适应性。(C) 2002 Elsevier Science Ltd.版权所有。
The aim of this two-part work is to propose a model for the corrosion mechanism of ferrous alloys in high-temperature aqueous environments. In the first part of the work, experimental results of the electrochemical behaviour of pure Fe, pure Cr, Fe-12% Cr alloy and Fe-25%Cr alloy during the initial stage of oxide film formation at 200 degreesC are compared to those obtained at room temperature. The results have been obtained by using voltarnmetry, electrochemical impedance spectroscopy (EIS), contact electric resistance (CER) and contact electric impedance (CEI) techniques. An increase of temperature from room temperature up to 200 degreesC has been found to result in higher currents in the passive region for all the materials. The CER, EIS and CEI results indicate that the film especially on Fe is considerably thicker at the higher temperature. In addition, the EIS and CEI results give information of an ionic transport process at 200 degreesC, which has not been observed in the EIS response at room temperature. The dependence of the electrical and transport properties of the film on potential suggests that the films at 200 degreesC can also be described by a mixed-conduction model (MCM) introduced recently for room temperature. However, the faster rate of ionic defect transport has to be emphasised at the higher temperature. The adaptation of the MCM to high-temperature oxide films is discussed in more detail in the second part of this work. (C) 2002 Elsevier Science Ltd. All rights reserved.