Evaluation of the open-circuit overpotential decay behaviour of a previously polarized electrode provides a useful way of examining the kinetics of the electrode reaction and the electrochemical adsorption behaviour of reaction intermediates involved in the electrode process. Limiting cases have previously been considered. Analytical and numerical solutions of equations for the open-circuit decay of potential of a polarized electrode are now given for a complete range of coverages of the electrode by electro-active intermediates arising in a complex sequence and obeying a Frumkin-type isotherm. The behavior for various values of the interaction/heterogeneity factor g in the adsorption isotherm is derived. The course of the potential-log (time) relations for various g values are compared with the experimental behavior observed in chlorine evolution on C and Ir. The overpotential decay and the Tafel slopes are closely related to the adsorption pseudo-capacitance behaviour of the electrode interface bearing electroactive chemisorbed intermediates.