Objective Buried oil and gas pipelines are typically safeguarded by both anti-corrosive coating and cathodic protection. However, over time, the anti-corrosive coating degrades and may peel off during extended operation. High IR drop in the crevice results in uneven distribution of protection current, making it challenging for the cathodic protection current to penetrate the depth of the crevice. This often results in inadequate protection of the pipeline in the crevice within the peeling zone. Pulsed current cathodic protection (PCCP) offers superior advantages over traditional methods and provides enhanced protection for pipelines in high-resistance medium environments. At present, the comprehensive understanding on the mechanism of PCCP is inadequate, prompting the need for further research to validate its applicability in systems with peeled anti-corrosive coating.

Methods A study was conducted using a crevice simulation experimental device to analyze the polarization behavior of pipelines with peeled anti-corrosive coatings under PCCP, along with the influence of parameters such as the protective potential, pulse frequency, cathodic protection duty cycle, and crevice clearance on the protection effect.

Results The polarization potential gradient generated by PCCP was mainly concentrated near the seam of the peeling zone due to its shielding effect. As the depth of peeling increased, the potential within the crevice shifted positively, eventually nearing the free corrosion potential.

Conclusion Compared with conventional cathodic protection, PCCP can improve the local potential and current distribution in the peeling zone, thus extending the effective protection range in the zone. The effective protection depth beneath the peeled coating increases with the negative shift of the cathodic protection potential Ecp and the drop of the local potential in the crevice. Higher pulse frequency and duty cycle prolong the duration of pulsed cathode polarization, leading to decreased charging and discharging current of the electrical double layer in the cathode current. This enhances the effective protection current, thereby improving cathodic polarization levels and extending the effective protection range within the peeling zone. Due to its lower current requirement, PCCP enables a more uniform potential distribution, consequently extending the effective protection range.