Experimental and numerical studies of effectiveness of cathodic protection at corrosion defects on pipelines

• Develop a numerical model to simulate potential and current density at defects.
• Determine the potential distribution inside the defect under cathodic protection.
• Evaluate effectiveness of cathodic protection at defects on pipelines.
• Derive empirical equations for corrosion defect assessment.

In this work, the effectiveness of cathodic protection (CP) at corrosion defects on an X100 steel pipeline was investigated both experimentally and numerically. A finite element model was developed to simulate distributions of local potential and anodic/cathodic current density inside the defect. Results demonstrated that there is a non-uniform potential and current distribution at corrosion defects. The CP is shielded, at least partially, at the defect, especially at its bottom. This effect is enhanced with increasing depth and decreasing width of the defect. Empirical equations are derived to enable calculation of CP effectiveness at corrosion defects, providing industry recommendations for accurate assessment of further corrosion allowance and remaining life of pipelines in the field.