A First Principles Based Approach to Potential Attenuation Projection for Marine Pipelines and Risers

Cathodic protection (cp) design and analysis tools for one dimensional systems such as pipelines and risers are reviewed with emphasis being given to newly proposed, first-principles based potential attenuation and anode/anode bed current output equations that incorporate all relevant resistance terms (anode (electrolyte), coating, polarization, and metallic path). One of the new expressions pertains to pipelines with superimposed (bracelet) anodes and a second to the case where the anode/anode bed is offset from the pipeline, as occurs for buried onshore pipelines and marine pipeline cp retrofits and pipelines deployed by reeling. In effect, the former (superimposed anode) is a special case of the latter. It is demonstrated that the expressions can be employed to analyze both galvanic and impressed current cp systems. Comparisons are made between the potential attenuation projected by the present expression and by the classical equations of Morgan/Uhlig. It is concluded that the Morgan/Uhlig approach is non-conservative in cases where the pipeline, or a portion thereof, lies within the anode potential field.