Steel is the most widely used material for pipelines from water supply storages to reticulation networks. Predicting its service-life performance is therefore critical to avoid catastrophic failure and interruptions to supply. Current lifetime prediction models rely on the development of accelerated metal-soil electrochemical tests and correlation of data with in-service performance. Existing methods are limited because they are carried out under pre-determined moisture levels and provide little or no detail about the depth dependence of corrosion performance. In this work an experimental test column has been used for electrochemical testing of mild steel coupons at various sample depths under specific conditions of moisture content. The final column design ensured that reliable contact was maintained between the metal surface and the soil. The corrosion rate of coupons at the top of the column varies considerably with drying and three distinct regions of corrosivity can be mapped; highly corroding, not corroding and a third, intermediate, transition region which is defined by slope (k). The corrosion rate of coupons at the bottom of the column is less dependent on moisture loss and is regulated by oxygen diffusion through the above soil. At a critical moisture content oxygen diffusion causes acceleration of corrosion processes at the bottom of the column. Corrosion rate measurements from this investigation may be integrated into existing models, to assist better predictions of asset failure, initially for unprotected steel pipes, but possibly extending to coated and cathodically protected pipes.
Accelerated test based on eis to predict buried steel pipe corrosion
2013
12 Seiten, 10 Bilder, 5 Tabellen, 12 Quellen
Conference paper
Storage medium
English
New corrosion detection method for buried pipe lines - Part 2
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