Corrosion of carbon steel and the passivating properties of corrosion films formed under high-PT geothermal conditions.
Corrosion of carbon steel and the passivating properties of corrosion films formed under high-PT geothermal conditions.
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DOI：
10.1016/j.scitotenv.2019.04.386
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
N. Mundhenk;K. Knauss;S. Bandaru;R. Wonneberger;T. Devine
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文献类型：
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作者：
N. Mundhenk;K. Knauss;S. Bandaru;R. Wonneberger;T. Devine
腐蚀是安全实施岩土工程应用的主要障碍。利用垂直扫描干涉测量（VSI）和电化学阻抗谱（EIS）的新方法，我们讨论了在二氧化碳饱和的温和酸性单键cl盐水中，在地热相关温度（80-160 °C）下碳钢腐蚀和膜形成的时间依赖性。铁溶解动力学在80和160 °C时呈对数速率，在120 °C时呈线性速率。在80 °C时，较高的初始腐蚀速率（前24 h）产生H2at，最小速率为12 μmol h−1cm−2，并形成连续的~100 μm厚的多孔腐蚀膜。该材料呈双相结构，外层为结晶状FeCO3层，内层由Fe3C骨架网络浸渍FeCO3组成。作为电导体，我们假设Fe3C通过提供额外的阴极位置来强烈提高腐蚀速率。在120和160 °C时观察到由阳极成膜反应（可能是Fe-oxide）引起的伪钝化，随后在120 °C时发生点蚀。160 °C时的稳态腐蚀速率比120 °C时至少低一个数量级。我们的实验方法证明了在研究腐蚀相关现象方面具有普遍适用性的潜力。
Corrosion is a major obstacle to a safe implementation of geotechnical applications. Using a novel approach that includes vertical scanning interferometry (VSI) and electrochemical impedance spectroscopy (EIS) we discuss time-dependent carbon steel corrosion and film formation at geothermally relevant temperatures (80–160 °C) in CO2-saturated mildly acidic Nasingle bondCl brine. Iron dissolution kinetics follows a logarithmic rate at 80 and 160 °C and a linear rate at 120 °C. At 80 °C, high initial corrosion rates (first 24 h) generate H2at a minimum rate of 12 μmol h−1cm−2and lead to the formation of a continuous ~100 μm thick porous corrosion film. It exhibits a duplex structure with a crystalline outer FeCO3layer and an inner layer composed of a skeletal network of Fe3C impregnated with FeCO3. Being an electrical conductor we hypothesize the Fe3C to strongly enhance corrosion rates by providing additional cathodic sites. Pseudo-passivity due to an anodic film-forming reaction (presumably Fe-oxide) was observed at 120 and 160 °C, soon followed by the initiation of pitting at 120 °C. Steady-state corrosion rates at 160 °C are at least one order of magnitude lower than for 120 °C. Our experimental approach demonstrated potential for general applicability in studying corrosion-related phenomena.