Corrosion Behavior of X80 Pipeline Steel under Coupling Effect of Stress and Stray Current

Abstract

In this work, the coupling effect of stress and stray current on corrosion of X80 pipeline steel was investigated in soil-simulating solution by open circuit potential (OCP) and corrosion potential test, potentiodynamic polarization measurement and surface characterisation technique. A mathematical relationship between corrosion rate and yield strength, direct current (DC) stray current density was obtained through multiple linear regression. The results indicate that, the corrosion potential of X80 pipeline steel with and without superimposed DC stray current all shift negatively, and the corrosion rate increases with the enhancement of tensile stress in solution. Moreover, the above laws become increasingly obvious with DC stray current density form 0.5 to 3.5 mA/cm2. Comparing with the stress, the effect of stray current on corrosion rate of X80 pipeline steel is more significant in elastic deformation. Mutation in corrosion potential and corrosion rate appeared when the strain reaches plastic deformation. This study provides important recommendations for pipeline safety design and operation, where the corrosion enhancement due to the coupling effect of stress and stray current should be considered.