Corrosion behavior of the heat affected zone in a 316 L pipeline weld

On-site investigation, scanning electron microscope, energy dispersive X-ray spectroscopy, and cyclic potentiodynamic polarization test were carried out for failure analysis of the 316 L pipeline in this paper. The visual inspection revealed that the inner wall was covered with severe rust, and obvious misalignment and poor appearance were found in the weld. The energy dispersive X-ray spectroscopy result identified the presence of Cl in the inner wall of the pipeline. Some carbides of Cr and Mo precipitated in the heat affected zone, which partially deteriorated the corrosion resistance. The cyclic potentiodynamic polarization curve proved that the heat affected zone is not only sensitive to pitting corrosion, but also has inferior repassivation ability. Finally, the pitting preferentially occurred in the heat affected zone and gradually developed to leakage.