Bottom of Line Corrosion Mechanism in Marginal Sour Environment Wet Gas Pipelines

Internal pipeline corrosion is a well-recognized issue in the oil and gas industry, especially in multiphase flow systems, such as wet gas transportation pipelines that contain mixed phases. Internal corrosion typically manifests as either top-of-the-line corrosion (TLC) or bottom-of-the-line corrosion (BLC). While corrosion mechanisms in sweet environments (dominated by CO₂) are relatively well-understood, those in sour environments (dominated by H₂S) remain less thoroughly examined. In sour environments, the primary corrosion product is iron sulfide (FeS), while in sweet environments, iron carbonate (FeCO₃) tends to form. In marginally sour conditions, FeS layers are often non-uniform, promoting localized corrosion and pitting because low concentration of H 2 S. It is hypothesizes that higher concentrations of H₂S reduce both the pitting rate and depth.The objective of this research is to investigate the corrosion rate, surface profile, and morphology in a marginal sour environment, using profilometry analysis (ASTM G46) to assess pitting. The experiments were conducted in a glass cell setup simulating pipeline conditions with 3 wt% brine solution and 1000 ppm acetic acid. Corrosion behavior was assessed at H₂S concentrations of 0 ppm, 30 ppm, and 80 ppm using weight loss analysis, surface morphology, and profilometry measurements. Results indicate that increasing H₂S concentration decreases the pitting rate, supporting the study’s hypothesis.