Geothermal wells are a feasible energy source to replace fossil fuel supply. Hence, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities. However, some additional aspects might rise.

During circulation tests at the geothermal research facility in Groß Schönebeck (Germany), massive copper precipitation has been observed downhole clogging the production well. Occurring mechanisms and measures to prevent copper precipitation or scaling needed to be investigated.

This contribution deals with the evaluation of the corrosion behavior of different metals ranging from carbon steel via stainless and duplex steels to titanium in a copper containing artificial geothermal water, simulating the conditions in the Northern German Basin, using electrochemical measurements and exposure tests. While carbon steel exhibits copper deposition (scaling) and copper precipitation, higher alloyed materials show different response to Cu-species in saline geothermal water. Here, no relevant formation of insoluble Cu-species could be detected.

Based on these results, the suitability of the investigated high alloyed materials and Ti-alloy can be concluded for use in such conditions, as long as no crevice conditions in combination with non-metallic parts occur. Carbon steel is not recommended to be used.

Subject
Geothermal energy, Water, Materials, Precipitation (solids), Circuit potentials, Repassivation potentials, Electrochemical testing, Open circuits, Steel, Pitting, Carbon steel, Copper, Corrosion potential
Keywords:
copper, corrosion, steel, geothermal energy
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2019
Association for Materials Protection and Performance (AMPP)
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