Influence of Bicarbonate Ions on the Stability of Prepassive Layers Formed on Copper in Carbonate-Bicarbonate Buffers

The dissolution and passivation of polycrystalline copper (Cu) electrodes in carbonate (CO32−)-bicarbonate (HCO3−) solutions covering wide ranges of pH and electrolyte compositions were studied at 25°C. The influences of the CO32−−HCO3−concentration ratio and hydrodynamic conditions on electrodissolution of the base metal, on formation of prepassivating and passivating surface layers, and on chemical dissolution of the prepassive films were considered. Results obtained with a rotating disc electrode allowed the competing reactions related to the active-to-passive transition to be distinguished through the effects of potential scan rate and electrode rotation speed on the electrochemical behavior of the system at fixed concentrations of CO32− or HCO3−. Data were discussed on the basis of the interactions between HCO3− and Cu(II) oxide and hydroxide anodic products in the prepassive surface layer.