The interest for evaluating the effectiveness of cathodic protection (CP) systems is still considerable. The - 850 mV-Cu/CuSO4 polarized potential for underground structures is the recommended practice
but in some situations, conventional off-potential measurements are not feasible or inaccurate. The use of corrosion coupon resolves some problems occurring during simple off-potential measurements but all
these methods only determine the effectiveness of the cathodic protection by off-potential measurements. The real corrosion rate of the cathodically protected structure cannot be determined. This paper presents results ffi'om an underground corrosion probe that provides direct measurements of the corrosion rate in soil. The corrosion probe, located near a pipe, is periodically connected to the CP system of the pipe to perform CP off/CP on cycles. The high resolution and high accuracy of these underground corrosion probes allow measurements of soil corrosivity and control of the effectiveness of the CP system.
Keywords: cathodic protection, corrosion rate measurement, corrosion monitoring, corrosion probe, corrosion coupon, pipeline.