The electrodissolution of cobalt in carbonate/bicarbonate solutions was studied at room temperature by steady state polarisation, interfacial pH measurements and Raman spectroscopy. The active dissolution of cobalt leads to an initial CoO film formation. The CO32- metal passivation occurs by a slow transformation of the CoO into a Co3O4 oxide. The influence of HCO3- and CO32- anions was investigated. Two different parallel electrochemical processes were proposed to account for the anion role on the electrochemical steady state behaviour of cobalt in the studied solutions.