Effect of pulse cathodic protection on corrosion mitigation and electrochemical conditions under a simulated coating disbondment on pipeline steel

Abstract

Coating disbondments on pipeline steels are regions with high resistivity where conventional cathodic protection (CP) could not fully protect. Therefore, in an attempt to mitigate this challenge, this study investigates the effect of pulse CP on corrosion mitigation and electrochemical conditions under a simulated coating disbondment on X-52 pipeline steel. In this regard, conventional and pulse CP of −870 mV SCE were applied to the open mouth of a simulated coating disbondment.For pulse CP, frequencies of 1, 5, and 10 kHz were used. Results showed while the conventional CP was not able to fully protect the 20 cm simulated coating disbondment, for the pulse CP with increase in frequency from 1 to 5 kHz, and from 5 to 10 kHz, improve in CP potential protection under the simulated coating disbondment was achieved. This was accompanied by considerably lower corrosion and a more uniform pH distribution under the simulated coating disbondment.

Long‐term cathodic disbondment tests in three‐layer polyethylene coatings

“…[9,10] This lack of effectiveness is given by a process named cathodic protection shielding, where cathodic current cannot flow adequately due to mass transfer issues. [11,12] The literature provides insightful analysis regarding the variables that affect organic coatings delamination, [4,13,14] cathodic protection shielding, [8,12] and techniques to evaluate corrosion due to disbondment, [5,15] evidencing the damages caused to the coating and the metal. However, besides mainly dealing with laboratory studies and immersion in aqueous solutions, which might not be extended to actual cases of buried pipes, there is a literature gap on the effect of patching pipes with different coating matrixes, which is a common practice where pipe sections with old damaged coatings must be replaced for new ones.…”