Optimization of Cathodic Protection Systems of Tank Bottoms Using Boundary Elements, Inverse Analysis, and Genetic Algorithm

The required current to efficiently protect the external bottom of aboveground storage tanks by means of impressed current cathodic protection was evaluated and optimized for anode number and positioning. The study introduced a numerical polarization curve obtained by inverse analysis, using a genetic algorithm, based on potential values measured in a real tank. An inverse boundary element-based genetic algorithm was developed to find the expected polarization curve from potential values measured in situ. To the problem optimization, an axisymmetric boundary element with a Newton-Raphson solution algorithm was used to accommodate the nonlinear boundary conditions. The system consisted of a tank directly over soil or a slender conductive concrete support layer. Impressed current anodes were positioned between the base and a secondary liner containment installed below the tank to prevent environmental damages in case of leakage. An alternative technique was adopted to analyze the two-region problem. Here a single soil region, with a calculated modified polarization curve was chosen, avoiding the two subregion analysis needed to represent the concrete layer and soil.