Evaluation of internal corrosion property in district heating pipeline using fracture mechanics and electrochemical acceleration kinetics

The corrosion of district heating (DH) pipelines in the internal environment is carefully controlled, however the long-terms of corrosion induced fracture is still uncertain. The general corrosion of pipeline in the heating water is very moderate, therefore it is almost not affected to initiate fracture. While, localized corrosion in weld zone is very dangerous situation because it can act as a stress concentration point. Therefore, it is significant to analyze using the fracture mechanics whether a fracture actually occurs due to the localized corrosion or not. In this study, the long-term corrosion was simulated using the electrochemical acceleration method. The surface morphology parameter of the accelerated specimen was analyzed using a 3D profiler. The crack tip opening displacement (CTOD) was calculated using the corrosion morphology parameters. Consequently, in internal DH environment, general corrosion is the dominant factor in fracture rather than localized corrosion. In other words, internal corrosion cannot be a main reason of the DH pipeline fracture.