FEM Simulation Analysis of the Pipe-Casing Under Cathodic Protection

In the present study, pipe-casing under cathodic protection is modeled by using FEM. The inner and outer surface of the casing and coating defects at the pipe surface is considered as corrosion and protection interface that follows non-linear polarization behavior. The coating of casing, electrolyte resistivity in pipe-casing space and electrical resistivity between pipe-casing are the main variables. FEM model is approved by tens centimeters of the pipe-casing section experimental setup. After proofing the FEM model, it is scaled up to study more realistic dimensions and broader variable ranges. The FEM simulations show that when the casing is bare and electrically isolated from the pipe, coating defects of the pipe are easily protected in a wide range of solution resistivity in pipe-casing space. If pipe-casing resistance is reduced to lower than 10 ohms, the cathodic protection nullified, and corrosion could happen on the pipe coating defects. The presence of a coating on the inner surface of the casing will only lead to localization of the corrosion on its defects. Lower solution resistivity leads to an overall flattening of the potential distribution to an average value.