La dissolution du chlorure cuivreux formé par oxydation électrochimique du cuivre

Abstract

We have studied the dissolution of copper chloride formed by the electrochemical oxidation of copper immersed in aqueous lithium chloride. The pH was maintained between 3 and 5 while the concentration of LiCl in solution was varied between 2.36 × 10−2 M to 16.5 × 10−2 M. The corrosion product accumulating on the electrode consists of crystals of nantokite (CuCl) formed by precipitation.The presence of this precipitate contributes to the local enrichment of the solution which is close to saturation near the electrode. This enrichment is revealed by an electrode voltage in a well characterized open circuit. This current is about −40 mV (/ECS) on a stationary electrode. The complete dissolution of CuCl coincides with a rapid drop in voltage which allows the transition time τ to be defined from which the speed of dissolution of CuCl has been calculated. For example, the speed of dissolution is 0.15 ± 0.01 mC s−1 cm2 in a current equivalent for a stationary electrode in the presence of 2.36 × 10−2 M of dissolved LiCl. This is also constant until the complete disappearance of the precipitate.In another study, the use of a rotating disc electrode shows that the dissolution is completely dominated by the diffusion of ionic species in the liquid phase. The experimental results are compatible with the presence of CuCl2− as the diffusing species. [Journal Translation]