Internal Corrosion Causes of a CO₂-Containing Wet Natural Gas Long-Transmission Pipeline and Its Prevention Measures

Aiming at the internal corrosion problem of a CO₂-containing wet natural gas long-transmission pipeline, the internal corrosion causes of the pipeline were clarified by investigating the pipeline operation conditions, observing the corrosion morphology and analyzing the composition of corrosion products, and the internal corrosion prevention and control measures of this type of natural gas pipeline were proposed. The results showed that due to the lack of strict control of the natural gas dew point of the pipeline, when the ambient temperature was low and the temperature of the transported gas was relatively high, the condensate liquid film or droplets might appear on the inner wall of the pipeline. The settlement of the condensate water caused water accumulation in some low-lying sections of the pipeline, and CO₂ dissolved in the liquid water to form a strong corrosive carbonic acid, resulting in CO₂ corrosion. At the same time, in the process of pipeline hydraulic test, the test water was not deoxygenated and sterilized. After the end of the hydraulic test, the pipeline was not cleaned and dried in time, which would lead to water accumulation before the pipeline was put into operation, resulting in dissolved oxygen corrosion and bacterial corrosion.