For the reduction of greenhouse gas emissions in the global energy production, geothermal energy is one of the promising ways. Due to the high corrosivity and scaling ability of geothermal fluids, the selection of proper metallic materials is a big challenge for its reliable development. One of the main scientific issues of the project is the understanding of the crack initiation and propagation mechanisms in the confined space at the mineral scale/steel interface. Use of the new experimental platform CorRTEx gives an unique chance to reproduce the temperature and pressure range of geothermal plants (up to 350 °C and 200 bar). The first technical Task 1 will consist of implementing a heat-exchanger system with electrochemical monitoring devices inside the HP-HT recirculating autoclave of the CorRTEx loop to control mineral scale formation at the surface subjected to the heat-transfer. The circulation of a heating/cooling fluid inside the tube will create favorable conditions for the precipitation of minerals at the heat-exchanger tube's external surface. At the end of this task, fully operational HP-HT equipment will be available for the scientific study of Task 2 that will study the impact of brines compositions, field conditions on scale formation and localized corrosion. The mineral deposits will be characterized according to global and local electrochemical methodologies. Another important parameter that will consider is the microstructural state of the material which conditions its reactivity: a passivating alloy will be a stainless steel type 316 with or without work hardening, and carbon steels with a ferrito-perlitic (J55) and a tempered martensite structure (P110) will be selected. Hence physical and chemical characteristics of the scales and oxide (passive) layer will be evaluated. Two methods will be used to promote surface scaling. The first one that will be performed on both a laboratory and on the CorRTEx loops will be the application of a thermal gradient. The second laboratory method is inspired by geosciences studies: the tube blocking test consists of using two test solutions, the first one containing the precipitable anion, while the second one contains the precipitable cation. From mixing these two solutions, high saturation ratios may be obtained to promote a fast precipitation.The obtained results will enable to understand (i) kinetics of scale formation at different test conditions, (ii) composition of the scales and (pseudo-)passive (oxide) layer, (iii) localized corrosion mechanisms addressing (pseudo-)passive films and mineral scales formation, which will allow adapting localized corrosion models to geothermal environments. This task's results will represent direct inputs for Task 4 dedicated to the study of the effect of scales on stress corrosion cracking (SCC) and the modeling. In order to study this effect on SCC under static and dynamic imposed strain-rate loading conditions, Task 3 will implement a tensile machine in the CorRTEx loop with electrochemical measurements. As very little information is available in the literature, Task 4 aims to understand the impact of mineral scales on the different stages in the evolution of localized corrosion defects towards stress corrosion cracks with stable growth which both depend on the local corrosive media at the crack tip. 3D orientation microscopy, EBSD, EDS data will be used to study the microstructure and crystallography's influence on the nucleation of cracks, their growth rate, and their path. Dissolution-assisted propagation models based on the crack tip strain rate will be revisited. In Task 5, particular attention will be devoted to the dissemination of the results for both general, technical and scientific audiences. A part of this task is dedicated to the edition of recommendation on best practices for selecting corrosion-resistant materials to increase safety and reliability of geothermal energy productions will be issued.