Investigation of corrosion effect on underground metal pipes

Underground metal pipes are essential infrastructure for water, oil and gas transport. The presence of localized pitting corrosion has been identified as one of the main deterioration mechanisms for this pipe material. These corroded pipes, when exposed to external loadings, can easily fail due to intensified stresses at the corrosion pits. Disruptions to pipelines not only greatly affect the life of citizens, but also cause severe economic loss and safety risk, and hence, accurate prediction of safe design life of buried pipes becomes significant. The main objective of this paper is to investigate the effect of corrosion on bearing capacity of corroded pipes. Two types of exhumed pipes made of cast iron and steel were used for parallel-plate loading tests. The corrosion parameters of the corroded pipes were thoroughly examined by various techniques, such as 3D scanning measurements and secondary electron microscopy (SEM). The results showed a significant reduction of rupture modulus of the cast iron pipes with the increase of exposure time and corrosion depth. This research work will enhance the current knowledge on corrosion to better understand the deterioration of metal pipes for facilitating safe life prediction of buried pipelines.