Impact of mineral deposits on CO2 corrosion of carbon steel

Abstract

Solid deposits are frequently encountered in oil and gas flowlines and are often related to causing premature pipeline failures by enhancing the internal corrosion process. In presence of accumulated deposits, the integrity of the carbon steel structures is affected even when supplemented with high performance CO2 corrosion inhibitors due to the complex phenomenon of under-deposit corrosion.The present study describes the impact of mineral deposits (SiO2, Al2O3 and CaCO3) on CO2 corrosion of 1030 carbon steel in chloride-containing environment. The corrosion process was investigated using electrochemical and weight loss methods, followed by surface analysis of the corroded steels conducted by visible light microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was found that the extent of the corrosion damage is directly related to the nature of the mineral deposits and significant differences were noticed in the morphology of the surfaces corroded in the presence/absence of various deposits. The susceptibility of the deposit covered surfaces to the localized corrosion and the integration of corrosion inhibition measures are also discussed and related to the properties of the deposits. The study serves to improve the understanding of CO2 corrosion process in the presence of solid deposits and the findings can be applied to address the under-deposit corrosion in oilfield operations.