A finite element based model for prediction of corrosion defect growth on pipelines

Growth of corrosion defects has been identified as the primary mechanism resulting in pipeline perforation and leaking. In this work, a finite element model was developed to simulate and predict the time-dependent growth of corrosion defects on pipelines in a near-neutral pH bicarbonate solution trapped under disbonded coating. The synergism of stress and local corrosion reaction was determined quantitatively. It is demonstrated that a mechano-electrochemical effect developed at the defect is critical to growth of the defect, resulting in formation of a crack-like flaw at the defect center. The time dependence of the local stress and corrosion current density at the defect is featured with three stages, i.e., a linear increase of local elastic stress and the negligible corrosion enhancement under the testing condition, a slow increase of both local stress and corrosion current density under mild plastic deformation, and a rapid increase of local stress and corrosion current density under a high plastic deformation.