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Internal corrosion is one of the primary mechanisms resulting in pipeline failures. Statistics showed that, of the various reasons causing failures of gathering pipelines in Canada, internal corrosion was responsible for nearly 55% of all failure events. For long-distance transmission pipelines, internal corrosion occurring under deposit (e.g., petroleum sludge, sand bed and corrosion products) can result in pipeline leaking, especially in the presence of microorganism.

Internal corrosion of pipelines is a complex phenomenon, and the complexity arises from the fact that multiple chemical and electrochemical reactions occur simultaneously in the environment where numerous factors affecting the corrosion processes have interrelated each other. This talk includes contents which are based the author’s extensive research experiences and interactions with industry in the last two decades. A thermodynamic model was developed to determine the electrochemical anodic and cathodic reactions occurring during internal corrosion of pipelines under given conditions. Parametric effects such as solution pH, CO₂ partial pressure, temperature, etc. were considered. In addition to uniform corrosion, localized corrosion under deposit is paid much attention. The unique role of microorganism, particularly sulphate-reducing bacteria (SRB), in pipeline corrosion was investigated. Numerical models were developed by integration of electrochemical corrosion with fluid hydrodynamics in the pipeline, enabling prediction of the location of corrosion occurrence and the corrosion rate over a long-term period of service.