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.
Keywords: Corrosion, pitting, in-situ monitoring, corrosion inhibitors, sour ga