IR correction : Part II. Effect on corrosion monitoring

Abstract

The effect of iR drop on the corrosion rates obtained by curve fitting of the polarisation data around the corrosion potential is an increase in the corrosion current calculated, which is in direct contrast to linear polarisation measurements. The b a values and, for an activation-controlled cathodic process the b c values, are increased by added ohmic resistance, R u. This more than offsets the increase in R p and so the i corr increases. For a diffusion-controlled cathodic process the b c becomes negative with added R u. All the results are not unduly affected by up to ±2% random error. A current-interrupt method of iR correction has been used for steel corroding in a deaerated H 2SO 4 solution to demonstrate the effect of iR correction.