Numerical and electrochemical analyses on carbon dioxide corrosion of X80 pipeline steel under different water film thicknesses in NACE solution

Abstract

Gas-liquid flow in a wet gas pipeline with low liquid loading was studied by computational fluid dynamics (CFD) simulation. Eulerian wall film model was used to calculate the formation and development of water film on the wall of large diameter pipe. Based on the water film thickness obtained by CFD, carbon dioxide corrosion of X80 pipeline steel under water film of NACE solution was investigated using a wire beam electrode (WBE). It was found that secondary flow promoted water film fluctuations. The distribution of water film became wider as the elbow angle was increased. The total anodic current density decreased slightly and then became stabilized ultimately as water film thickness was increased from 648 μm to 2500 μm. The distributions of large cathodic regions and small anodic regions were formed. Maximal anodic current density was observed at 350 μm. When the water film thickness was less than 350 μm, FeCO3 was easily formed and anodic current density decreased. The distributions of large anodic regions and small cathodic regions were found. The side walls of the elbow and the impact walls of the vertical pipe downstream of the elbow faced a high risk of mesa attack due to different water film thicknesses.