Research on Corrosion Factors and Anti-corrosion Measures of Surface Gathering and Transportation System for Deep Coalbed Methane

Aiming at the inner wall corrosion of ground gathering pipelines for deep coalbed methane, the composition and distribution of corrosion products were systematically analyzed, the driving mechanism and influencing factors of corrosion were discussed, and the application effects of corrosion inhibitors were evaluated. The results show that the corrosion products on the inner wall of the L245N pipeline are mainly composed of iron oxide and calcium carbonate, and the content of calcium carbonate decreases from outside to inside, while the content of iron oxide increases. The corrosion process is mainly driven by the oxidation reaction of iron, and the high calcium ion concentration in the produced water is the main cause of calcium carbonate scaling. Environmental factors such as increased temperature, increased Cl^- concentration, the presence of dissolved oxygen, and the Fe³⁺/Fe²⁺redox cycle all accelerate the corrosion rate. Hydroxyethylidene diphosphonic acid（HEDP） exhibits excellent corrosion inhibition in oxygen-free environment, but its efficiency decreases in oxygen-rich environment. 304 stainless steel shows good corrosion resistance and stability in an oxygen-rich environment. HEDP inhibits the dissolution of iron by forming a protective film, and its mechanism is mainly anode inhibition, which significantly improves the electrochemical stability of the material. The adsorption energy of HEDP on the surface of Fe（110） is negative, and the absolute adsorption energy decreases significantly with the increase of the temperature.