Analysis of Corrosion Behavior and Cathodic Protection of Steel Pipeline Under Alternating Current Interference

Alternating current (AC)-induced corrosion poses a significant threat to the integrity of underground pipelines, making it a critical concern for pipeline infrastructure. This study investigated the corrosion behavior of protected pipelines subjected to AC interference and developed practical tools to determine the required cathodic protection (CP) measures. Numerical models were developed to simulate current distributions in pipelines, incorporating the effects of metal types, CP levels, and varying AC interferences. These models were rigorously validated and calibrated using laboratory experiments to ensure their reliability. The models were then employed to analyze the corrosion behavior of pipeline metals under diverse CP and AC conditions. The results revealed the critical role of AC interference in aggravating corrosion rates and the diminishing effectiveness of CP at higher AC levels. Additionally, the study highlights the material-dependent nature of corrosion, with X60 pipe steel demonstrating superior resistance compared to C1018 pipe steel. Under the same AC and CP levels, the corrosion rate for C1018 pipe steel is 1.85 to 3.65 times higher than that for X60 pipe steel. Based on numerical analysis, empirical equations were developed to optimize the control of corrosion rates for both C1018 and X60 pipe steels under varying AC and CP conditions. The CP current density required to mitigate corrosion under an AC interference of 50 A/m2 is 1.45 A/m2 for C1018 pipe steel and 0.18 A/m2 for X60 pipe steel. As AC interference increases to 500 A/m2, the required CP current density rises to 2.98 A/m2 for C1018 pipe steel and 2.2 A/m2 for X60 pipe steel, highlighting the increasing demand for cathodic protection at higher AC levels.