Cathodic protection modeling of marine pipelines

A governing equation for potential attenuation along a pipeline cathodically protected by identical, evenly-spaced, spherical anodes is developed. The numerical solution, obtained using a coordinate based mapping (CoMB) finite difference method (FDM), can be used to predict the potential profile of a pipeline. In addition, a modified version of Ohm's Law is developed to provide an improved approach to design of pipeline CP systems. Both approaches address anode-electrolyte, coating-polarization, and metallic path resistance, but the latter neglects to address the potential gradient associated with the one-dimensional nature of pipelines. These two approaches were compared to results from existing potential prediction methods and Boundary Element Methods (BEM). Furthermore, a procedure was developed to calculate the resistance of rectangular conductor arrays. This procedure was utilized to calculate the resistance of an anode sled. Combination of the first principles based equation and the rectangular array resistance procedure allows one to predict the potential profile for a pipeline protected by identical, evenly-spaced, anode sleds.