A novel evaluation technique, based on an artificial pit electrode, has been developed for inhibitor studies. The first example is of three generic inhibitors, against localised corrosion. The second is of three industrial inhibitors against existing localised corrosion on a north sea production platform
02288 2002 CP
J. Marsh, J. W. Palmer and R. C. Newman
Corrosion inhibitor tests typically evaluate performance with respect to general corrosion. However, pipeline failures in oil and gas production are predominantly caused by localised corrosion, not general corrosion. A novel evaluation technique, based on an artificial pit electrode, has been developed for inhibitor studies. Two examples of its application are presented. The first is a determination of the relative effectiveness of three generic inhibitors, a quaternary amine, a phosphate ester and oleic imidazoline, against localised corrosion in a slightly sour environment. The second is an assessment, using similar techniques, of three industrial inhibitors for use against existing localised corrosion on a north sea production platform subject to barium sulphate scaling of the topside pipework. In both cases the tests were able to discriminate between inhibitors which gave similar levels of protection against general corrosion. It was also found that prevention/mitigation of existing localised corrosion required far higher inhibitor concentrations than general corrosion, and inhibitor efficiency could not easily be increased beyond 75%.
Keywords: Corrosion inhibitors, offshore oil production, localised corrosion