PARSC 019 – Potential Impact of Abandoned Anode Beds

January 2019

Executive Summary

Petroleum Technology Alliance Canada (PTAC), through the Pipeline Abandonment Research Steering Committee (PARSC), has commissioned various research topics covering different facets related to abandonment of pipelines. PARSC 019 was commissioned to develop a best practice surrounding the abandonment of cathodic protection anode beds. The main activities involved with this proposal will be based on completing a review of available information about the topic and formulating first steps at approaching the topic of anode bed abandonment.

To assist in the prevention of corrosion to exposed steel on below grade pipelines, cathodic protection (CP) systems are installed. CP systems can be split into two (2) categories: including impressed current cathodic protection (ICCP), or galvanic (sometimes referred to as sacrificial systems). ICCP system require an external current source to function while galvanic systems do not.

ICCP systems will typically include a current source such as a rectifier or DC controller which is connected to both the structure to be protected and the installed anode beds via cabling. The external power source is used to impress driving voltage between the structure and the anodes which subsequently results in DC current flow, the magnitude of which is determined by the overall system circuit resistance. Galvanic CP systems, function by directly or indirectly connecting active anode material metals via cabling to the structure to be protected. For buried pipeline applications the galvanic anode material utilized is often zinc or magnesium. Where an ICCP system functions by impressing a DC driving voltage, galvanic systems function because of the natural DC voltage differences found between dissimilar metals. In the case of both ICCP and galvanic systems, the respective components create a system whereby the anodes are sacrificed and the target structure to be protected has its lifespan extended. It should be noted that on a case by case basis, various other components may be installed as part of an overall ICCP or galvanic system. These supplementary components may include but not be limited to electrical isolation devices, junction boxes, test posts, miscellaneous monitoring provisions, and remote monitoring units.

Final Report