Causes of Internal Corrosion of a Gas Pipeline in Daniudi Gas Field

The causes of internal corrosion of the external pipeline of a gas gathering station in Daniudi gas field were analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). The results showed that the solid and liquid corrosion products was loose and porous structures, and the protective effect on metal matrix was poor. The main elements of the corrosion products were Fe, O, S and C, and the contents of C and S elements exceeded the standard. The corrosion products were mainly composed of FeS, FeCO₃, Fe₂O₃ and Fe₃O₄. The synergistic corrosion of H₂S and CO₂ occurred in the gas pipeline. H₂S and CO₂ dissolved in the condensate water deposited in the pipeline and reacted with the metal matrix. The main corrosion form was localized corrosion.