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Corrosion Behavior of High-Alloy Austenitic Stainless Steel in Simulated Geothermal Environment

Drilling deeper geothermal wells to obtain more energy output per well with higher temperature and pressure and increased corrosiveness. Testing was done in simulated geothermal environment at 180°C and 350°C with a pressure of 10 bar. On high alloy austenitic stainless steel UNS S31254.

Product Number: 51317--9280-SG
ISBN: 9280 2017 CP
Author: Sigrun Karlsdottir
Publication Date: 2017
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$20.00
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In recent years there has been an increased interest in drilling deeper geothermal wells to obtain more energy output per well with the corresponding higher temperature and pressure and increased corrosiveness of the geothermal environment. To explore the potential of the high alloy austenitic stainless steel UNS S31254 in future deep geothermal wells corrosion testing was done in simulated geothermal environment at 180°C and 350°C with a pressure of 10 bar. The simulated environment was composed of steam with H2S HCl and CO2 gases with a pH of 3 upon condensation. The testing was done in a flow through reactor for a 1 and 3 week exposures. The UNS S31254 performed well at 180°C with negligible corrosion rate both for the 1 and 3 week test and no localized corrosion damages were detected. Interestingly large NaCl were detected on the surface after testing. After the testing at 350°C localized damage were observed on the surface of the samples and substantial amount of NaCl crystals had formed on the surface. Microstructural and chemical composition analysis revealed large cracks in the cross-section of the sample possibly due to chloride induced stress corrosion cracking. The measured corrosion rate for the 1 and 3 week test was 0.024 mm/year and 0.24 mm/year respectively.

Key words: laboratory testing, simulated geothermal environment, high temperature, stress corrosion, cracking, UNS S31254.

In recent years there has been an increased interest in drilling deeper geothermal wells to obtain more energy output per well with the corresponding higher temperature and pressure and increased corrosiveness of the geothermal environment. To explore the potential of the high alloy austenitic stainless steel UNS S31254 in future deep geothermal wells corrosion testing was done in simulated geothermal environment at 180°C and 350°C with a pressure of 10 bar. The simulated environment was composed of steam with H2S HCl and CO2 gases with a pH of 3 upon condensation. The testing was done in a flow through reactor for a 1 and 3 week exposures. The UNS S31254 performed well at 180°C with negligible corrosion rate both for the 1 and 3 week test and no localized corrosion damages were detected. Interestingly large NaCl were detected on the surface after testing. After the testing at 350°C localized damage were observed on the surface of the samples and substantial amount of NaCl crystals had formed on the surface. Microstructural and chemical composition analysis revealed large cracks in the cross-section of the sample possibly due to chloride induced stress corrosion cracking. The measured corrosion rate for the 1 and 3 week test was 0.024 mm/year and 0.24 mm/year respectively.

Key words: laboratory testing, simulated geothermal environment, high temperature, stress corrosion, cracking, UNS S31254.

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09377 Evaluation of Corrosion Resistance for Materials in Geothermal Applications

Product Number: 51300-09377-SG
ISBN: 09377 2009 CP
Author: Markus Finke, Ralph Babler, Ali Saadat, Rolf Kirchheiner and Andreas Burkert
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