This study introduces the design and implementation of a bespoke electrochemical flow cell in combination with in-situ Synchrotron Radiation-X-Ray Diffraction measurements (SR-XRD). The system enables high precision, real-time, in-situ measurements of iron carbonate (FeCO3) evolution on carbon steel in a flowing environment, as well as providing real-time, in-situ corrosion rate measurement through an integrated three-electrode cell. The custom cell is used to examine FeCO3 formation kinetics in a carbon dioxide (CO2)-containing aqueous environment, particularly in instances where the ‘pseudo-passivation’ phenomenon is reported to occur. Linear polarization resistance and anodic polarization measurements were performed in combination with the SR-XRD measurements to establish a detailed understanding of FeCO3 formation in real time and its relation to the corrosion behavior of carbon steel. It was observed that ‘pseudo-passivation’ occurred in conjunction with the growth of a highly protective FeCO3 layer under all conditions evaluated. Magnetite (Fe3O4), an oxide layer often attributed to the onset of ‘pseudo-passivation’, was not observed in these conditions, despite the high limits of detection of the technique.