Investigation into the mechano-electrochemical interaction of internal and external corrosion defects on pipe surfaces

Abstract

Revealing the mechanical-electrochemical interactions (M-E) on internal and external defects in pipelines is of paramount importance for ensuring the safe operation of pipelines. The present study establishes a mechano-electrochemical multi-physics coupling model and develops a two-dimensional finite element (FE) model of internal and external defects on the pipe surface to investigate the M-E interaction of X100 steel pipe with corrosion defects on both internal and external surfaces. The results demonstrate that the M-E interaction is significantly influenced by the geometrical shape, relative position, and internal pressure of defects. Moreover, altering a single defect parameter can simultaneously impact the M-E interaction of two defects. As the depth of defects increases, the cross-sectional area between internal and external defects decreases, leading to an intensified interaction between mechanics and electromagnetics and a gradual concentration of M-E interaction at the center of defects. The magnitude of the M-E interaction exhibits a negative correlation with the length of the defect, while the presence of a long defect minimally impacts the M-E interaction on the opposing side. As the external defects gradually distance themselves from the internal defects, the M-E interaction diminishes and the concentration area of M-E interaction shifts in the opposite direction to defect migration, while stress in the non-defect region adjacent to both internal and external defects progressively intensifies. The increase in internal pressure significantly enhances the M-E interaction of internal and external defects, with the M-E interaction primarily focused on the minimum cross-sectional area of radial overlap between these defects. At low internal pressures, however, the M-E interaction becomes negligible.