One of the main challenges associated with the operation and maintenance of binary geothermal power plants is the degradation of construction materials. In this sense, it is crucial to apply appropriate preventive maintenance in critical components (such as the wellheads, heat exchangers, or pipes), while reducing shutdown times. Based on electrochemical measurements performed in an autoclave corrosion testing setup, we studied the corrosion mechanism of API L80 steel grade as a function of operational and/or maintenance procedures. We used a test fluid representative for a site in Switzerland, but the main observations made may be applicable in a wider context. We found that changes in the fluid temperature (from 200 to 100 °C) or temporary oxygen ingress significantly influenced the corrosion behavior of this carbon steel and increased its corrosion rate (from approx. 20 µm/year to > 120 µm/year). After a few days, the corrosion rate was found to decrease and stabilize around values of 50–70 µm/year, as a result of a porous corrosion product layer formed on the metal surface (approx. 250 µm thick). Electrochemical impedance spectroscopy indicated an increase in capacitance of the double layer over time, most likely due to an increase in the effective surface area of the steel sample, as a consequence of surface roughening due to corrosion. The results from this study may be implemented in the design and operation of future power plants in Switzerland and elsewhere to ensure reliable and cost-effective energy production from geothermal resources.

中文翻译：

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模拟地热电厂腐蚀的实验室测试：使用条件的影响

与二元地热发电厂的运行和维护相关的主要挑战之一是建筑材料的降解。从这个意义上讲，在减少停机时间的同时，对关键部件（例如井口，热交换器或管道）进行适当的预防性维护至关重要。基于在高压釜腐蚀测试装置中进行的电化学测量，我们研究了API L80钢种的腐蚀机理，该腐蚀机理是操作和/或维护程序的函数。我们在瑞士的某个地点使用了测试液的代表，但是所做的主要观察可能适用于更广泛的背景。我们发现，流体温度的变化（从200到100°C）或暂时的氧气进入会显着影响这种碳钢的腐蚀行为并提高其腐蚀速率（从大约20 µm /年到> 120 µm /年）。几天后，由于在金属表面上形成了多孔腐蚀产物层（约250 µm厚），发现腐蚀速率下降并稳定在50-70 µm /年左右。电化学阻抗谱表明双层电容随时间增加，这很可能是由于腐蚀引起的表面粗糙导致钢样品有效表面积增加所致。