In situ SR-XRD analysis of corrosion product formation during ‘pseudo-passivation’ of carbon steel in CO2-containing aqueous environments

In situ Synchrotron Radiation X-ray Diffraction (SR-XRD) is employed to follow the evolution of corrosion products on X65 carbon steel in a CO2-containing aqueous environment (80 °C, pH 6.3-7.3). A custom-designed flow cell is used to follow the real-time concomitant changes in electrochemical behaviour and corrosion product growth during stages of both natural and potentiodynamically driven ‘pseudo-passivation’. We show that no deteca crystalline magnetite (Fe3O4) phase forms during ‘pseudo-passivation’ across all conditions studied. Furthermore, the results suggest the significant ennoblement observed during ‘pseudo-passivation’ in these experiments can be strongly related to the accumulation of iron carbonate (FeCO3) on the steel surface.