An elbow made from welded steel tube had become leaky along a well-defined line in the axial direction. The entire wall of the tube was corroded, and the longitudinally-welded seam stood out clearly as a result of particularly intensive corrosive attack. The appearance of the corroded surface indicates the action of water with a high oxygen content. The oxygen in the return water must have originated from the ventilation of the open expansion vessel. Because of the corrosion-favoring effect of a crevice, water with a high oxygen-content that was perhaps still warm or even hot found particularly favorable conditions...
Egon Kauczor, Leaky Socket Pipe from the Safety Return Circuit of a Heating Installation, ASM Failure Analysis Case Histories: Processing Errors and Defects, ASM International, 2019, https://doi.org/10.31399/asm.fach.process.c9001211
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