Corrosion deposition in deforming anodes of in-ground cathodic protection systems: A three-dimensional transient study

Cathodic protection as a complementary technique is widely considered in the industry along with the selection of suitable materials as well as efficient coating considerations. In cathodic protection (CP), anode produces a current output to protect the structure (cathode) and part of the current output is wasted by the grounding system. We developed a 3D, and time-dependent numerical model to simulate the anode corrosion (using arbitrary Lagrangian-Eulerian method), find the deposit formation (by interface tracking level set method), anode mass loss and current wasted by the grounding system. We also defined a CP efficiency as anode mass loss times the current percentage received by the structure. The CP efficiency can be utilized for anode quantity and placement pattern. The results showed when the conductivity of corrosion products (deposit) is lower than that of soil, the current output from the anode decreases over time. When the deposit conductivity is higher than that of soil, the current output from the anode increases in time, reaches a peak, then decreases. This is due to the competition among three factors: anode surface increase, medium conductivity change, and inhibition effect of the deposition layer. For the studied case, almost 54% of the current from the anode is wasted by the grounding system. To illustrate the significance of CP efficiency, this study compares three alternative anode configurations with the original design. It is observed that for a 14.5 kg anode, burying the anodes 2 m deeper enhances the mean potential distribution on the structure by 4%. Additionally, the configuration featuring the 7.7 kg anode, owing to its superior dimensional design, demonstrates improved performance compared to other configurations.