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 stead y-state (current-voltage curves for various disk rotation rates) and t ransient [frequency analysis of the electrochemical and electrohydrody namical (EHD) impedance] measurements. The anodic polarization curves have presented one region of mixed kinetic and another of mass-transpo rt control characterized by a current plateau. The limiting current is a OMEGA1/2 function throughout the whole range of rotation rates. Fro m the EHD impedance diagrams observed below the anodic plateau, it was shown that the limitation by mass transport is due to CuCl2-. On the current plateau, the presence of two time constants on the EHD impedan ce diagram and the reductibility of the curves have been attributed to the existence of a salt layer covering the surface, the rate of forma tion of this layer being identical to the rate of dissolution. A layer model has been developed.