engleski

Investigating internal corrosion of liquid hydrocarbon pipeline by various techniques

Within the framework of asset management as well as environmental protection, internal corrosion risk assessment is one of the most important activities of modern pipeline corrosion management. In order to assess the risk of corrosion in pipelines, it is important to understand corrosion mechanisms and be able to predict whether localised corrosion will be initiated and how it can be prevented. Internal corrosion in oil or gas carrying pipelines is generally influenced by temperature, CO2 and H2S content, chlorides, water chemistry, flow velocity, oil or water wetting and composition and surface condition of the steel. Besides these abiotic corrosive factors, the presence of bacteria is known to cause severe internal corrosion problems. Microbiologically influenced localised corrosion with very high corrosion rates of several millimetres per year is one of the most feared types of corrosion attack. In the present work we investigate sludge from the interior of the carbon steel crude oil pipeline sampled at the location where wall perforation due to corrosion has already occurred. The sludge sample was analysed by various techniques: FTIR, XRD and SEM/EDS. Bacterial analysis and chemical analysis of Cl- and SO42+ content were also preformed. The results indicate bacterial activity as the main root cause of the observed corrosion failure. It is exemplified that application of complementary techniques unveils a pattern specific to the corrosive action of biotic corrosive media. The methodology proposed in the work presents significant contribution to detecting microbiologically influenced internal corrosion and can be applied for determination of corrosion risk at locations where failures have not yet occurred.

corrosion menagement ; FTIR ; XRD ; bacterial analysis

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