Failure Analysis of an Unused Delivery Tube of Stainless Steel 316L

316L stainless steel has good resistance to pitting corrosion, but pitting failure can also occur under certain conditions. The reasons for the leakage of an unused 316L heating furnace tube were analyzed by macro analysis, chemical composition analysis, electron scanning microscopy (SEM), energy dispersive spectroscopy (EDS) and microstructure analysis. The results show that many Cl^- and Br^- ions were contained in the water used in hydraulic pressure test for the tube. After hydraulic pressure test, the tube was sealed before the water had been drained completely, resulting in the occurrence of pitting corrosion in storage period.