Cathodic Protection Systems Analysis for Aboveground Storage Tanks

Abstract Cathodic protection (CP) is widely used to protect against soil-side corrosion of aboveground storage tanks (ASTs). However, design practices, field installations and implementations, and operational parameters can be suboptimal, leading to soil-side corrosion of the AST bottoms even with CP in place. For example, in anode ring CP systems, the loop-to-loop separation distance requires that the entire bottom plate is adequately saturated with CP current. This requirement also means that the sandpad thickness must be considered during the system design phase, and failure to do so can lead to deficiencies in the design. Similarly, failure of the anode rings during operation may lead to suboptimal current distribution. Therefore, a CP current distribution model is needed to study design variables, field installation and implementation conditions, and operation parameters and their effects on the CP current distribution such that a given tank has optimal corrosion control. A finite element method was used to develop the CP current distribution model. The model was exercised for various options such as varying sandpad thickness across the pad surface and sandpad resistivity variations. The model results were used to develop CP design and installation guidelines for various configurations.