An iteration method for computing the nonuniform potential and current distributions at a partially passivated disk electrode is introduced. The computation method is developed for a small cathode in the vicinity of a much larger anode, a situation encountered in some polarized electrochemical systems, e.g., anodic protection. It uses the finite element method allied with a trial and error technique as well as a successive boundary condition variation technique. The method was used for the study of a steel electrode immersed in a 0.5 N HAc + 0.05 N NaAc solution. The computed distributions, currents, and radius of the passive center were in good agreement with the measured values.