Ballast Tank Cathodic Protection Shielding Effect

Based on some discussions on the mathematic model set up for the cathodic protection potential field, a two-dimensional boundary element method (BEM) is developed, and by using which, a study on the shielding effect resulted from some typical inner structures such as the reinforcing elements and the partition walls with man holes on distribution of potential and current density in the cathodic protection is performed. The investigated parameters which affect the shielding effect in the calculating model include: the height and thickness of the reinforcing elements, the distance between the anode and the reinforcing elements, and the diameter of man hole on the partition walls, and so on. From the simulating calculated results for several ideal models, some important views for practical design of cathodic protection are achieved. The calculated results show that it is impossible to realize a reliable design of the cathodic protection for a ballast bank because of the shielding effect resulted from many inner structures on protection current. In order to design a reliable cathodic protection system for a ballast bank, it is necessary to develop a quantitative model for the shielding effect due to the inner structures on the protection current in a cathodic protection system of a ballast tank through a lot of numerical simulation or practical measure.