Corrosion Monitoring using Polarisation Resistance Measurements: II. Sources of error

Abstract

The various fundamental and experimental factors which contribute to inaccuracy in, or even invalidate, the polarisation resistance technique of monitoring corrosion rates, are reviewed. The factors include deviations from linearity of polarisation data in the vicinity of the corrosion potential, polarisation data obtained close to reversible potentials, the presence of appreciable IR drops, failure to achieve steady state during polarisation, time-dependent corrosion potentials and Tafel slopes, electrode perturbation, and probe element differences resulting from localised corrosion. An attempt is made to assess the various factors in terms of the possible magnitudes of errors introduced into calculated corrosion rates.