September 2016 - Nathan Muncaster discusses the phenomenon of Cathodic Shielding.
In 2015, NACE formed a new task group - TG523 - the role of which was to clarify and define the mechanisms that cause pipeline coatings to shield cathodic protection (CP), and to enhance the industry's understanding of the topic.
Whether or not a pipeline coating shields CP is determined by the following: during the coating's failure mode, CP currents are unable to reach the substrate adequately. This is shielding the CP. Through this seems straight forward, the particulars of how this occurs can vary depending on materials. A common misunderstanding is to link the shielding of CP to proper electrical insulation, which is a different topic. [read more...]