Finite element modeling of local corrosion accelerated by the mechano-electrochemical coupling effect at defects on pipelines under combined effects of internal pressure and axial applied stress

Abstract

A finite element model was built to assess the combined effects of internal pressure and axial applied stress$\left( {\sigma_{A} } \right)$ on localized stress concentration and electrochemical corrosion at defects on pipelines under the mechano-electrochemical (M-E) interaction. When defect angle $\alpha$ (i.e., included angle between the major axis of the defect and longitudinal direction of the pipe) is 90°, the maximum stress of the defect is enlarged remarkably with the increase in $\sigma_{A}$, leading to electrochemical corrosion at the defect affected greatly under the M-E interaction. However, when $\alpha$ is 0°, the maximum stress and electrochemical corrosion are affected slightly by the $\sigma_{A}$. Besides, when the hoop stress of the pipe is larger than its total axial stress, the largest corrosion rate at the defect with $\alpha$ of 0° would be higher than that at the defect with $\alpha$ of 90°. Thus, for the improvement of pipeline integrity management, the combined effects of internal pressure and $\sigma_{A}$ should be taken into account for a more accurate prediction of local corrosion rate at the defect especially with $\alpha$ of 90°.