Modeling of the mechano-electrochemical effect at corrosion defect with varied inclinations on oil/gas pipelines

Abstract

A 3-dimensional finite element model was built to determine the effect of inclination angle of a corrosion defect on local mechano-electrochemical (M-E) effect in a simulated soil solution. Because of the high effect of the defect inclination angle on the M-E effect, when the inclination angle is 0° (i.e., the primary axis of the defect parallel to the longitudinal direction of the pipe), the greatest stress concentration level at the defect can be observed, which is associated with the lowest corrosion potential, the greatest anodic current density and the most serious accelerated localized corrosion. When the inclination angle is 90°, the stress concentration level reduces and the corrosion potential becomes less negative, accompanying with the decreased anodic/cathodic current densities. Besides, when the ratio ( r ca ) of the primary axial length of the defect to its secondary axial length is 1, the defect inclination does not affect the stress and the electrochemical corrosion rate at the defect. With the increase of r ca , the effect of the defect inclination angle is more apparent.