Magnetic field effects on copper electrolysis

The effect of a static magnetic field, B, on the electrolysis of copper in aqueous solution is investigated using linear sweep voltammetry, impedance spectroscopy, chronoamperometry, rotating disk voltammetry, and analysis of fractal growth patterns. Data are obtained in fields of up to 6 T. There i s a large enhancement of the electrodeposition rate (up to 300%) from conce ntrated CuSO4 solution (c similar to1 M) when pH less than or equal to 1. T he effect of the magnetic field is equivalent to that achieved by rotating the electrode. From the pH, viscosity, field direction and concentration de pendence of the field effect, the influence of field on the complex impedan ce, and the equivalence of field and electrode rotation, it is established that the magnetic field influences mass transport by forced convection. Con vective flow is modified on a microscopic scale in the boundary layer close to the working electrode. There is no influence on the electrode kinetics. Turbulence sets in for our cell geometry when the product of field and cur rent density exceeds a critical value of about 1000. N/m(3). The competitio n between gravitational and magnetic forces is dramatically exhibited by th e morphology and fractal dimensionality of planar electrodeposits in a flat circular cell. Quantitative comparison is made of the magnitude of various magnetic body forces inducing convection in typical experimental condition s. The results are discussed both in terms of Aogaki's model of a streamlin e boundary layer, which predicts that the excess limiting current varies as B(1/3)c(4/3), as observed experimentally, and in terms of the electrokinet ic effect.