Approaches to overcoming ongoing pipeline corrosion monitoring challenges

Steel pipelines are susceptible to corrosion when installed underground, especially when they are under the effect of factors such as stray currents or disbonded coatings. These factors generally increase the risk of corrosion because they could locally nullify cathodic protection (CP). Corrosion monitoring, if performed properly, can help enhance the safe and economical operation of pipelines, by providing a means of inexpensively collecting site-specific and in-situ corrosion information at any required time and frequency. The capability of corrosion monitoring to complement corrosion inspection techniques is well accepted, however, its practical application in complex industrial conditions, especially in heterogeneous systems such as underground pipelines, has been limited. Unlike conventional inspection techniques, corrosion monitoring measures corrosion happening on the pipeline surface indirectly. It measures what is occurring on the surfaces of the corrosion probes, based on the principle that corrosion occurring on a large structure such as a pipeline would also occur on a smaller probe made of the same material and exposed to the same environmental condition. Nevertheless, ensuring that the key elements of the corrosion processes affecting a large and complex structure are simulated by strategically designed and located discrete probes is currently an unsurpassed challenge. A rational strategy must be developed to ensure the reliability of the collected information using corrosion probes. In this paper, the application of corrosion monitoring in heterogeneous conditions and several factors affecting the design and location of corrosion monitoring probes for early warning of external corrosion on buried pipelines have been discussed. It is concluded that in order to ensure the reliability and accuracy of corrosion monitoring as an early warning tool, three general rules should be observed in order to ensure that the probes are capable of simulating the worst possible corrosion situation along the monitored structure, and collecting information regarding the maximum corrosion rate on their own surface.