GEOSTEELCOR

The development of geothermal energy is one of the most promising ways to reduce greenhouse gas emissions. Due to the high corrosivity of geothermal fluids and their power to form mineral deposits, the selection of suitable metallic materials is a challenge for its development. One of the main scientific challenges addressed by the project is understanding the mechanisms of initiation and propagation of cracks at the mineral deposit/steel interface.

Using the new CorRTEx platform offers a unique chance to replicate the temperature and pressure range of geothermal operations (up to 350°C and 200 bar). A heat exchanger system equipped with electrochemical measurements will be installed inside the CorRTEx loop to control the formation of deposits. The impact of brine compositions and geothermal field conditions on the formation of deposits and localized corrosion of carbon and stainless steels will be studied in the laboratory and in the CorRTEx loop, using global and local electrochemical methodologies and fine electrochemical characterizations of steel-mineral deposit interfaces.

In order to study the phenomena of stress corrosion cracking (SCC) under imposed loading and strain rate conditions (static and dynamic), a mechanical stressing device, associated with electrochemical measurements will be installed in the CorRTEx loop. The impact of mineral deposits on the different stages of the evolution of localized surface corrosion towards CSC cracks will be investigated. 3D microscopy, EBSD, EDS data will be used to study the influence of microstructure and crystallography on crack nucleation, their propagation speed and their trajectory. Dissolution-assisted propagation models, based on the crack tip strain rate, will be revisited. Particular attention will be devoted to the dissemination of the results both to the general public and to the technical and scientific public, notably through the publication of recommendations on best practices for the selection of corrosion-resistant materials to increase the safety and reliability of systems. geothermal energy production.