Synergistic effect of stray current and stress on corrosion of API X65 steel

The effect of stray current and stress on corrosion of API X65 steel in simulated solution of the alkaline soil in Daqing in China was investigated using corrosion potential test, potentiodynamic polarization measurement, as well as surface analysis techniques. A mathematical relationship between corrosion rate and yield strength, direct current (DC) stray current density was obtained by multiple linear regression. The results demonstrate that, the corrosion potential of API X65 steel with and without superimposed DC stray current all shifted negatively, and the corrosion current density increases with the enhancement of tensile stress in solution. The corrosion current density under the synergistic effect of stress and stray current is much higher than corrosion current density that single factor (stress or stray current) induced. Comparing with the stress, the effect of stray current on corrosion rate of API X65 steel is more significant in elastic deformation. Mutation in corrosion potential and corrosion rate appeared when the strain reaches plastic deformation. This work provides reference suggestion for pipeline safety design and operation, where the corrosion enhancement due to the synergistic effect of stray current and stress should be considered.