Modeling Pipeline Corrosion with Holiday and Disbonded Coating under Cathodic Protection

Abstract For pipelines equipped with both cathodic protection and coating coverage, cathodic disbondment has been recognized as a significant factor that adversely affects the long-term integrity of pipelines. Due to experimental constraints, developing a numerical model to study disbonded coating systems is crucial for understanding the mechanisms of cathodic disbondment and for preventing its occurrence and subsequent coating failure. To achieve a more comprehensive and accurate simulation of cathodic disbondment, a model system incorporating both holiday and disbondment components was established in this study. The effect of cathodic protection (CP) level was investigated using the current density of iron dissolution to assess corrosion intensity and pH to evaluate disbondment development tendency. More negative CP potentials resulted in lower current density and higher pH levels, indicating better protection but with the potential risk of over-alkalization in the disbondment area. Significant differences were observed between holiday and disbondment areas, with the latter showing more pronounced changes.