THE CURRENT-DENSITY DISTRIBUTION ON STATIONARY WIRE ELECTRODES DURINGCOPPER AND LEAD ELECTRODEPOSITION

The current density distribution during lead and copper electrodeposit ion on to stationary copper wire electrodes was investigated by inspec tion of the morphology of the deposit. It was shown that the tip curre nt density was much larger than that on the rest of the electrode duri ng deposition from low conductive solutions. In contrast, the current densities are practically the same for the deposition from solutions c haracterized by large conductivity. A mechanism of transformation of O hmic potential drop in the homogeneous current field in electrochemica l overpotential at the edge of a plane and the tip of a wire electrode is proposed by considering the current line dissipation between the c athode edge, tip, anode and cell walls. There are a large number of cu rrent lines between two symmetrically-positioned points on the edges ( assumed as lines) of the anode and cathode making the Ohmic drop along each of them negligible. Because of this the electrochemical overpote ntials and current densities at these points must increase in order to compensate the Ohmic drop between two symmetrical points in a homogen eous field on the anode and cathode. The above reasoning is obviously valid for the tip of a wire electrode (assumed as a point) because the dissipation of current lines in this case takes place through space w hile in the parallel plane electrode arrangements it takes place in on e plane normal to the electrodes to which two symmetrically-positioned points belong. (C) 1997 Elsevier Science B.V.