The Error in Polarization Resistance and Capacitance Measurements Resulting from Nonuniform Ohmic Potential Drop to Flush-Mounted Probes^⋆

The possibility of encountering a systematic error in polarization resistance measurements resulting from the nonuniform ohmic potential drop to flush-mounted electrodes is investigated. The error is introduced even though the ohmic potential drop is considered by use of the interrupter technique or by measurement of AC impedance at high frequencies. The error is significant when the ohmic potential drop is large, for example, in the presence of high corrosion rates and low-conductivity solutions. Correction factors are calculated for a disk electrode immersed in a bulk electrolyte or covered by a thin film of conducting solution.