High-rate copper dissolution in hydrochloric acid solution

The dissolution of copper in 1 M chloride solution was studied by steady-state (current-potential curves for various disk rotation rates) and transient measurements [frequency analysis of the electrochemical and electrohydrodynamical (EHD) impedance]. The anodic polarization curves present four regions according to the potential: one region of mixed kinetics followed by another of mass-transport control characterized by one plateau, followed by a second mixed kinetics region and a second plateau. The results obtained for the first domain of mixed kinetics and for the first plateau were previously published. In this work, the second mixed kinetics region is considered. From the analysis of the ac and EHD impedance measurements, it was shown that a transition between the presence and the absence of a CuCl salt layer occurs at a critical 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 reactions is demonstrated.