The effect of addition of thiourea on the kinetics of anodic dissolution and cathodic reaction on copper and iron in acidic sulfate solutions has been studied using potentiodynamic polarization measurements. The results obtained in the presence of thiourea indicate that it has a very strong influence on the kinetics of discharge processes at different metals. The presence of this organic compound led to decreasing exchange current densities and to changes of Tafel slopes. The phenomenon observed is most likely the consequence of strong adsorption of thiourea on the electrode surfaces of investigated metals.