Effect of unstable intermediates formation on concentration distributions over diffusion layer during anodic behavior of metal

Transport processes taking place during a metal anodic dissolution that accompanied by formation of the charged intermediate species are examined theoretically. Profiles of the component concentrations over the diffusion layer by quasi-equilibrium decomposition of intermediate species are calculated. It is shown that during the electrochemical process the anion’s concentration either increases or decreases as compared with its bulk value. What was the outcome depends on the stability constant of the complex species. For the first situation (increase in the anion’s concentration), analysis predicts the anion’s concentration limit depending on the stability constant of the intermediate particles. For the second case (decrease in the anion’s concentration), it is possible there is the limiting current value because of electroactive anion depletion in the near-electrode layer.