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Validation of corrosion monitoring sensors through accelerated disbonded coating corrosion testing

Paper Number: 85
Author/s: F. Varela1, M. Forsyth1 and Y. Tan1
Organisation: Deakin University, Geelong, Australia, Institute for Frontier Materials and School of Engineering1

Abstract

Disbonded coatings are a major concern for the pipeline industry because not only they could give place to several forms of localized external corrosion, but also because they are extremely difficult to locate, identify and evaluate through above surface surveys. In order to ensure the safe operation of pipelines, the corrosion produced by disbonded coatings is managed through in-line inspection. Unfortunately, in-line inspection is expensive, not always applicable and requires significant meal loss before corrosion can be detected.
In recent years electrode arrays had been proposed as the basis for a corrosion monitoring system capable of replicate disbonded coatings and instantly measure corrosion rates. The information collected by these sensors could help prioritizing sections for in-line inspections or dig up locations in the case of non-inspectable pipelines.
The data collected by the first few electrode arrays installed in the field, together with more fundamental laboratory studies suggested that wet/dry cycles are of critical importance for the initiation of corrosion under disbonded coatings. A large scale laboratory setup that makes use of this insight to accelerate corrosion under disbonded coatings in a controlled and representative manner was built. This work presents the results obtained with such experimental setup. The information collected allowed to validate the electrode array measurements against the actual corrosion produced on its surface and on a simulated pipeline. In addition, the electrode array performance was contrasted against commercial electrical resistance probes designed for pipelines.