Abstract
The dissolution of cuprous bromide, formed by the electrochemical oxidation of copper immersed in aqueous NaBr, has been studied. NaBr concentration was varied between 0.1 and 1.2 M at pH 4. The corrosion product accumulating on the electrode is crystalline γ-CuBr. The presence of this material contributes to the local enrichment of dissolved copper close to the electrode. This enrichment leads to a characteristic electrode voltage in open circuit, which is about −149 mV (ECS) at a stationary electrode immersed in a solution of 0.2 M NaBr. The complete dissolution of CuBr coincides with a rapid fall in voltage which permits the definition of the transition time τ from which the speed of CuBr dissolution has been calculated. For example, the speed of dissolution is 0.074 ± 0.003 mA cm−2 in a current equivalent for a stationary electrode in the presence of a non-stirred solution of 0.2 M NaBr. This is constant until the complete disappearance of the CuBr. On the other hand, use of a rotating disc electrode demonstrates that the dissolution is entirely dominated by the diffusion of ions in the liquid phase. The experimental results are compatible with the simultaneous presence of [Formula: see text] and [Formula: see text] as diffusing species. Finally, the potentiodynamic polarization curves show two oxidation waves. A non-negligible portion of the dissolution current, if not almost all, is associated with the formation of CuBr as the sole corrosion product on the electrode. [Journal translation]
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