Laboratory Results of Corrosion Tests for EGS Soultz Geothermal Wells

Abstract

Corrosion risk for the materials (casing, pipes) proposed for the Soultz project at 200°C was evaluated in laboratory in order to estimate the corrosion rate before the beginning of the geothermal power plant running. After a short review about the both corrosion and scaling works done at Soultz, detail laboratory experiments are fully described and interpreted in high temperature conditions. The tested materials were: steels TU42BT, P110, N80, steel with Sakaphen coating, and steel with two types of Teflon coating. The corrosion tests showed that carbon steel TU42BT corroded at 2 mm/y at 200°C. The corrosion products formed on the surface did not provide any corrosion protection. All the tested coatings performed very well. They effectively reduced the corrosion and they did not deteriorate during the test. Mexel inhibitor, which was tested in the past on-site but at lower temperature (<150°C) did not give any significant inhibitor effect at 200°C. The corrosion rate for TU42BT steel was nearly the same with and without the inhibitor indicating that new generation inhibitor must be recommended. The outside top part of the casing was investigated for microbiological corrosion.