Mechanistic Modelling of Hydrogen Sulphide and Carbon Dioxide Corrosion of Pipes Conveying Petroleum Crude-Oil and Gas

摘要

Although, corrosion of pipelines conveying petroleum crude-oil and gas is an electrochemical process, it however, involves several chemical reactions occurring in the bulk solution, prior to the surface of the metal. The occurrence of these chemical reactions can alter significantly the rate of the electrochemical processes at the metal’s surface; especially when as a result of high local concentrations of reacting species, the solubility limit of the product formed (iron carbonate or/and iron sulphide) is exceeded and the precipitation of inhibiting surface films occurs on the metal’s surface. Thus, this paper investigated the effects of the chemical reactions on the rate of corrosion of steel pipes conveying petroleum crude-oil and gas with the presence of hydrogen sulphide (H2S) and carbon dioxide (CO2). The results affirmed what were reported in the literature that corrosion of steel pipes is as a result of the formation of acidic solution due to the transportation of hydrogen sulphide (H2S), carbon dioxide (CO2) and water along with the crude oil and gas. In addition, it also ascertained that corrosion severity depends on the pH of the solution, and the higher the pH value, the less severe the corrosion. In other words, corrosion occurs at a faster rate in acidic pH, compared to neutral and alkaline pH. It further established that H2S corrosion is more severe than that of CO2, and also, pipeline corrosion could be catastrophic leading to failures of pipelines and environmental pollution, etc. due to open cracks formed.