Quantitative evaluation method for cathodic protection polarisation coupon

Abstract

With the many advantages of instantaneous off measurement, the polarisation coupon has become increasingly popular in the true polarisation potential reading of different cathodic protection systems. As a general rule, polarisation coupons are installed close to the reference electrode to reduce the error in potential measurement. As a result, the error in the potential reading for close coupons is low. Still, the mentioned error has not been quantified due to the coupon's geometry, direction and non-linear polarisation behaviour complexity. In the present work, the IR-Drop error as a function of current density is extracted with generic calculation and simple assumptions, and the results are checked with three possible coupon-reference electrode arrangements. The proposed calculation could be used to extract the intrinsic error of polarisation coupons, regardless of their arrangement and coupon size. Moreover, it could be used to correct the measured potential and extract the true structure-to-soil potential.