Abstract
Cathodic shielding of pipeline coatings is an important issue among coatings specialists and suppliers but may be one of the most misunderstood yet talked about phenomenon in the pipe coatings marketplace. It is not clearly defined in real terms but certain industry codes and standards define characteristics of pipeline coatings that are desirable attributes. However, those attributes result in a coating that could be interpreted as a coating that "shields". Generally all coatings are electrically resistive however resistivity levels vary depending on the coating technology employed and the conditions of service. Electrically resistive coatings, or otherwise referred to as high dielectric strength coatings, have a unique place in the industry but should not be misrepresented as being a negative because of their ability to resist the flow of cathodic current.
This discussion paper will summarize what various national and international codes and standards say about coating attributes and review test methods which are used to measure resistivity. This will relate specifically to electrical resistivity of coatings and look at the said attributes of the coatings with respect to how the codes and standards comment on shielding, if at all. The paper will also look at independent testing along with manufacturer and user sponsored research into coatings and their electrical interaction.
