Taking electrochemical system non-linearity into consideration, theoretical expressions are given that relate the error in the electrode polarization resistance measured using a frequency response analyzer to the successive derivatives of the steady-state current vs. potential characteristic. Applications to various electrochemical models are presented : the Butler-Volmer law, the Stern relationship for metal corrosion processes, reversible or irreversible electron transfer for redox reactions studied on rotating disk electrodes and metal dissolution-passivation reactions. Non-linear impedance measurements are carried out on an electrochemical redox system to support the theory.