HIGH-RATE COPPER DISSOLUTION IN HYDROCHLORIC-ACID SOLUTION

The dissolution of copper in 1 M chloride solution was studied by stea dy-state (current-potential curves for various disk rotation rates) an d transient measurements [frequency analysis of the electrochemical an d electrohydrodynamical (EHD) impedance]. The anodic polarization curv es present four regions according to the potential: one region of mixe d kinetics followed by another of mass-transport control characterized by one plateau, followed by a second mixed kinetics region and a seco nd plateau. The results obtained for the first domain of mixed kinetic s and for the first plateau were previously published. In this work, t he second mixed kinetics region is considered. From the analysis of th e ac and EHD impedance measurements, it was shown that a transition be tween the presence and the absence of a CuCl salt layer occurs at a cr itical potential. The value of this critical potential depends on the rotation rate; the higher the rotation rate, the higher the potential value. A model of kinetic dissolution for this transition is presented , and a coupling between the currents corresponding to the two reactio ns is demonstrated.