The quartz microbalance has been used in dynamic regime in order to obtain information on the mass relaxation after a perturbation of the polarization current. When the current is sinusoidally perturbed, the simultaneous analysis of the potential and mass sinusoidal responses allow the impedance and a mass-voltage transfer function to be measured. New data on the adsorbed intermediates can be attained, among them the surface coverage and the atomic weight. Experiments on copper dissolution and copper deposition in sulfuric medium under current control have shown the feasibility of this new technique.