In situ investigation of CO2 corrosion in Cr-containing steels in CO2-saturated salt solution at elevated temperatures and pressures

•CO2 corrosion was studied for FeCr alloys at high temperature and pressure.•Microscopy was used to characterize surface changes.•Raman spectroscopy was used to investigate corrosion products.•Cr(OH)3 and Fe2CrO4 film formed on surface hindered corrosion. To clarify the effect of Cr on CO2 corrosions at elevated temperatures and pressures, Cr-containing FeCr alloys were characterized by their surface changes and corrosion products in CO2-saturated 5 mass% NaCl solution at 3 MPa and a temperature range 100–200 °C. As the Cr content increased, FeCO3 content decreased and the surface of the steel exhibited interference colour due to the formation of a film containing Cr(OH)3 and spinel iron oxide, as determined by Raman analysis. Chromium promoted the solubility and crystallinity of corrosion products. Corrosion improvement can be expected by precipitating fine corrosion products containing chromium from the onset of the corrosion process.