Soil corrosion monitoring near a pipeline under CP

Abstract

Electrochemical noise (EN), linear polarization resistance (LPR), and harmonic distortion analysis (HDA) were used with three-electrode probes to monitor the corrosion occurring in soil in dry and wet conditions near a gas pipeline under cathodic protection. The test site was a cathodic protection (CP) test station where impressed current CP was applied to a 2 in. (5.1 cm) diameter FBE coated steel pipe using an 84 in. (0.2 m) TA-2 high-silicon cast iron anode. Electrochemical measurements were made at three locations, two inside the CP field and one outside the CP field. Electrochemical measurements were first made with the CP system off to establish the baseline corrosion and then with increasing levels of CP. The degree of protection was based on polarized potential and the adequacy of protection was determined by depolarization measurements. CP of an adjacent pipeline did not affect the measurement of either corrosion rate or pitting factor when using buried soil corrosion probes and the EN, LPR, and HDA techniques