Investigation of iron dissolution mechanism in acidic solutions with and without dissolved CO2 – Part II: ToF-SIMS 3D mapping

ABSTRACT ToF-SIMS 3D mapping and depth profiling were used to study the anodic iron dissolution mechanisms of mild steel in chloride containing aqueous CO2 environments. The technique detected adsorbed hydroxide and chloride intermediates formed duringthe corrosion process, which is consistent with the proposed multi-path reaction mechanism for anodic iron dissolution reaction. Despite the presence of aqueous carbonic species and their observed effect on the kinetics of iron dissolution, no additional adsorbed intermediates have been detected in aqueous CO2 environments, indicating that carbonic species do not directly participate in the iron dissolution reaction. ToF-SIMS 3D mapping results on characterization of the specimens immersed in a chloride containing solution with and without CO2 suggest that one role of aqueous carbonic species CO2 could be to accelerate the adsorption of chloride ions and formation of chloride intermediates.