316L 不锈钢焊接接头在含 S-H₂S 环境中的 腐蚀行为

316L stainless steel is widely used in the sulfur-containing natural gas purification equipment and pipelines. But, its welded seam and heat-affected zone may pose a higher risk of corrosion, because of their lower resistance of corrosion refer to base material. Therefore, the corrosion resistance of 316L stainless steel in welded joints is crucial to guaranteeing the safe operation of the relevant equipment and pipelines. Herein, the corrosion behavior of the substrate, welded seam, and heat-affected zone of 316L stainless steel in a simulated service condition was investigated using weight loss method, ultra-depth three-dimensional scanning microscopy, and X-ray photoelectron spectroscopy (XPS). The composition and semiconductor properties of the formed passive films were characterized using XPS and the Mott-Schottky method. The results show that, when H₂ S is free, the steel exhibit very light corrosion, with a general corrosion rate of only 0.001~0.004 mm/a. The content of H₂ S correlates with the corrosion rate, as the H₂ S content increases, the corrosion rate also rises; for example, in conditions of 0.1 MPa H₂ S at 120^oC, the general corrosion rate of the welded seam, base material, and heat-affected zone is 0.316, 0.472, and 0.551 mm/a, respectively, and the localized corrosion rates is 86.590, 42.757, and 60.861 mm/a. At 90^oC and 1 MPa H₂ S, the general corrosion rate of them is 1.136, 1.001, and 0.861 mm/a, and the localized corrosion rateis 125.595, 90.297, and 124.291 mm/a. These results indicate that the welded seam is a high-risk area for localized corrosion, with the localized corrosion rate is approximately 1.4 to 2 times that of the base material. XPS results revealed that the main corrosion products were iron sulfides, iron oxides, and Cr(OH)₃. The analysis of the semiconductor properties of the formed passive films showed that the welded seam had the highest carrier concentration, making the passive film in this region more susceptible to damage, leading to an increased risk of localized corrosion.