Some Errors in Linear Polarization Measurements and Their Correction

The errors due to the use of the approximation $Icorr′=B′ΔI,$⁠, where B′ depends on anodic and cathodic Tafel slopes, in commercial corrosion current meters is shown to be due to the nonlinearity of the current-potential curve in the vicinity of the corrosion potential. These errors are calculated for various combinations of Tafel slopes. It is proposed to use the relationship I_corr = κΔI, where κ depends on Tafel slopes, sign, and magnitude of polarization. The values of κ are tabulated for various combinations of Tafel slopes and polarization of +10 and -10 mV. The proposed procedure leads to correct values of corrosion currents independent of the degree of nonlinearity of the polarization curve.