Mass-Transport Study for the Electrodissolution of Copper in 1M Hydrochloric Acid Solution by Impedance

The dissolution of copper in 1M chloride solution was studied by steady-state (current-voltage curv s for various disk rotation rates) and transient [frequency analysis of the electrochemical and electrohydrodynamical (EHD) impedance] measurements. The anodic polarization curves have presented one region of mixed kinetic and another of mass-transport control characterized by a current plateau. The limiting current is a tl 1/2 function throughout the whole range of rotation rates. From the EHD impedance diagrams observed below the anodic plateau, it was shown that the limitation by mass transport is due to CuCI~. On the current plateau, the presence of two time constants on the EHD impedance diagram and the reductibility of the curves have been attributed to the existence of a salt layer covering the surface, the rate of formation of this layer being identical to the rate of dissolution. A layer mode l has been developed. Anodic dissolution of copper in chloride media has prompted numerous tudies. 1-n The dissolution is mass-transport limited and leads to the formation of CuCI~. Nev-ertheless, the diffusion step was ascribed by different au-thors either to C]- transport o the surface " or to the transport 'of CuCI ~ to the bulk solution. 2-