Monitoring External Corrosion of a Pipeline Covered with a Polyolefin Tape Using Electrochemical Impedance Spectroscopy

The external corrosion of a pipeline buried or submerged under specific conditions was studied. The pipelines were made of API 5L X52 steel covered with polyolefin tape. The external corrosion of pipelines was studied without and with coating to emulate those that are in service. The study of the external corrosion of a buried pipeline was carried out in a sodium bentonite medium. The bentonite humidity percentage was modified to simulate in a better way the characteristics of real soil and the effect of this on the measurement of external corrosion was determined. The electrochemical technique used to measure the external corrosion in buried ducts was the electrochemical impedance spectroscopy. The results showed a resistance to corrosion with a value of 2.41 and 25.896 Ω cm 2 with a humidity percentage of 80% for sodium bentonite for bare and tape pipes, respectively. The corrosion resistance values when varying the separation distance of 14 and 23 cm from the reference electrode and the counter electrode were 2.41 Ω and 0.13 Ω cm 2 , being very close values, which also occurred for the tape pipe. This indicated the independence of the resistance with respect to the electrode separation.