Abstract
Pitting corrosion of pipelines remains a serious concern to operators in the oil and gas industry. Pitting is a particularly insidious and extremely rapid form of attack of a metal structure which can lead to unexpected system failures. The pipe wall can be perforated within a relatively short space of time with no appreciable metal loss on the pipeline as a whole. Corrosion inhibitors are widely used by operators to maintain asset integrity and their effect on controlling general corrosion to acceptable levels is easily demonstrated by the use of weight loss coupons or techniques such as linear polarisation resistance (LPR). However, up to 80 % of pipeline failures are ascribed to pitting but very few monitoring methods are capable to show this outcome. This paper discusses localised corrosion monitoring (LCM) technique which has been utilised to provide in-situ quantitative assessment of pitting corrosion under laboratory simulated wet sour gas operating conditions. The predicted pitting damage by LCM was subsequently verified using a calibrated white light interferometer (WLI). Examples of the assessment of corrosion inhibitors in terms of their pitting inhibition performance employing LCM and the WLI are provided.
