The Current Distribution in Electrochemical Cells

Abstract

ConclusionsThe current density distribution in electrochemical cell was considered in a new manner on the basis of equation of the electrode kinetics. In this way it was possible to illustrate the effect of deposition conditions, geometry of the system and kinetic parameters of deposition processes. Besides, three main problems of current density distribution in electrometallurgy were treated semiquantitatively. The edge effect in metal electrorefinning and electrowinning processes was discussed in details and it was shown that the dendritic growth at the edges of the electrodes can be avoided by keeping the deposition current density below some critical value, probably little larger than this corresponding to the end of the Tafel linearity. At this current density the less coarse deposit in the homogenous field without the dendrites at the edges of electrodes can be expected.The current density distribution in electroplating and electroforming were also treated semiquantitatively and it was shown that decrease of ohmic resistance of electrolyte and increase of the Tafel slope for the cathodic process improves it. Obviously, all above discussion is valid if the local values of limiting diffusion current density do not varies along electrode surface, i.e. if the effect of the hydrodynamics can be neglected. As a metter of fact, the diffusion layer thickness may vary along the electrode interface due to hydrodynamic conditions and cause the different deposition conditions. This phenomenon is treated elsewhere