Volume 6, Issue 3 (March 2009)
Electrochemical Impedance Spectroscopy Measurement during Cathodic Disbondment Experiment of Pipeline Coatings
Modified cathodic disbondment (CD) experiments were carried out over a period of 14 months using 13 coatings used to protect the external surfaces of oil and gas pipelines. During the experiments, electrochemical impedance spectroscopy (EIS) data were recorded, and after the experiments the cathodic disbondment area was measured. From the EIS data, the increase in coating capacitance was determined. Based on the comparison of coating capacitance values obtained from EIS data with the cathodic disbondment data, the coatings were broadly divided into three types: (1) high-performance coatings that did not disbond despite increasing coating capacitance; (2) poor-performance coatings that disbonded more than predicted from the increase in coating capacitance; and (3) average-performance coatings that disbonded at a rate proportional to the increase in coating capacitance.