Electrodeposition in highly viscous media: Experiments and simulations

Electrolyte viscosity plays an important role in ion transport. Here we study the effects of high viscosity variations in thin-layer electrochemical deposition (ECD) under constant-current conditions through experimental measurements and theoretical modelling. The viscosity was varied through glycerol and polymer additions and the tracking of convective fronts was performed through the use of optical and particle image velocimetry techniques with micron sized particles. The theoretical model, written in terms of dimensionless quantities, describes diffusive, migratory and convective ion transport in a fluid under constant-current conditions. Experiments reveal that as viscosity increases, convection decreases, while concentration gradients increase. These effects are more pronounced when the current increases. Theory and simulations predict that as viscosity increases, the Poisson and Reynolds numbers decrease whereas the Peclet and electric Grashof numbers increase. Therefore, electroconvection becomes more relevant.