Investigation of the evolution of an iron carbonate layer and its effect on localized corrosion of X65 carbon steel in CO2 corrosion environments

The general and localized corrosion of X65 carbon steel in CO2-saturated environments conducive to iron carbonate (FeCO3) formation has been studied using electrochemical measurements, together with post-test surface analysis. This research offers new insights into the evolution of FeCO3 layer and its link to the subsequent initiation and propagation of localized corrosion. We identify crevice-like regions forming at boundaries/edges of the FeCO3 crystals, which constitute the crystalline layer, where small cavities filled with electrolyte are restricted between developing crystals. It is apparent that such crevice-like features act as precursors to the localized/pitting corrosion on carbon steel over longer durations.