Reaction model for kinetic of cobalt dissolution in carbonate/bicarbonate media

Cobalt dissolution in a carbonate/bicarbonate media was studied in order to elucidate the kinetic of the metal corrosion processes. Steady-state polarization and electrochemical impedance measurements were carried out during the active metal dissolution at different electrode rotation speeds. A reaction mechanism is presented in order to explain the metal dissolution: cobalt electrodissolution starts with the formation of intermediate (CoHCO3)ads on the electrode surface, followed by the simultaneous formation of a Co(CO3)22- complex and the formation of a CoO film. Mass transport is characterised by diffusion of the Co(CO3)22-complex away from the electrode. The reaction model was validated by an accurate simulation of the experimental steady-state polarisation and impedance measurements.