Modeling of Impressed Current Cathodic Protection Anode Arrangements for Storage Tank Bottoms

Above ground tanks are frequently used for the storage of Oil & Gas products and they can present a challenge to design an optimum corrosion control system. The base of the tank lies on or near the surface of the ground and is in contact with the material used to support the tank and therefore presents a corrosion challenge. One method of protecting the bottom of a tank is by use of an impressed current cathodic protection (ICCP) system. There are a number of types of Cathodic Protection systems which are designed to protect the tank base in these circumstances. The details of the design of such a system are very important for optimal performance and also the cost, if a number of such systems are to be installed The consequence of a poor design can be uneven distribution of protection potential on the tank base or in the worst cases regions where corrosion of the tank base can take place. An over designed system on the other hand can have significant economic consequences both in terms of installation cost and running costs. Computer modeling is now widely used to optimize CP Designs and verify that the design of the cathodic protection (CP) system meets the design requirements. In this paper a modeling tool is presented which enables corrosion engineers to evaluate the performance of tank base CP systems by predicting the protection provided to the tank for a given CP design. The paper describes and discusses all aspects of the modeling methodology, which it then applies to several different design concepts.