AbstractThe functional dependence of current density and overpotential for an electrochemical process taking place at the interface between a “blocking” electrode and a solid electrolyte and whose rate determining step is the tangential diffusion over the interface was evaluated. — The conditions of applicability to such systems of the classical electrochemical kinetics were criticized. — In particular, it was put into evidence that, even in the case of a linear trend between the logarithm of the current density and overpotential, the extrapolation of the straight line portion to zero overpotential in some cases does not allow the determination of the value of the exchange current