Corrosion and scaling are some of the most common challenges in geothermal applications due to the complex brine chemistry combined with the high temperatures and pressures, and the gaseous components. To study mineral scaling at metallic surfaces, appropriate corrosion tests representing the real geothermal reservoir and operating conditions must be selected. This paper focus on the reconstruction of thermal gradients between geothermal fluids and the steel walls of wells and heat exchanger tubes, in laboratory and autoclave flow loop tests (up to 200°C and 300 bar), to simulate scaling and corrosion conditions. The implementation of an electrochemical measurement device makes it possible to monitor changes to the electrochemical behaviour of steel subjected to thermal gradients in these environments and so the corrosion response and in situ evolution of scales. Results from carbon steels (N80 and P110) and stainless steel (13Cr) in artificial geothermal brines representative of Dogger and Soultz geothermal wells in France are presented.