Failure Analysis of Localized Corrosion Perforation of an Oil and Gas Pipeline Dominated by CO2
DOI:
https://doi.org/10.54097/qqdggv98Keywords:
Oil and gas pipeline; CO₂ corrosion; pitting; perforation failure; ferrous carbonate; corrosion product film.Abstract
A systematic failure analysis has been carried out on a leaking part of an oil and gas pipeline that has suffered from internal pitting and perforation due to operation. Observe the general shape and, with the help of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS), determine the phases, microstructure and elemental distribution of the corrosion products. Based on the above results, the main corrosion product is ferrous carbonate (FeCO₃), which is a typical product of CO₂ corrosion. The corrosion product layer is porous and uncompacted, and there are many through-going cracks in the cross-section; thus, it cannot protect the steel below. Impurities in the transporting medium, such as chloride ions (Cl⁻), sulfides (S²⁻), calcium salts and silicates, constantly enter through the cracks and pores of the product film to reach the metal substrate. At the corrosion front, there are all kinds of cell occlusion, under-deposit corrosion and crevice corrosion, and as a result, local wall thinning and pitting perforation have occurred. The failure of the CO₂ corrosion product film due to the combined effect of many corrosive agents will result in a local perforation, and this paper will provide a reference for controlling corrosion in similar oil and gas pipelines.
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