Investigation on Probabilistic Model for Corrosion Failure Level of Buried Pipelines in Kirtipur Urban Areas (Nepal)

Abstract

Potable water supplies mostly through buried galvanized steel and cast-iron pipes from distribution terminals to the public, and a lot of corrosion failures occurred each year in urban cities of Nepal. It is an urgent need to know the main responsible factors for such buried metallic pipeline failures and subsequently evaluate the level of corrosion risk in soils of presently studied Kirtipur urban areas. Six factors (i.e., pH, moisture, resistivity, oxidation–reduction potential-ORP, chloride, and sulfate ions) of fifty-three soil samples were determined using American Standard for Testing and Materials (ASTM) standard. It estimates 6.4–7.9 pH, 7–45% moisture, 4.5 × 103–45.5 × 103 Ohm.cm resistivity, 317–514 mV ORP, 12–86 ppm chloride, and 40–294 ppm sulfate ions in the samples, indicating the soils of the Kirtipur urban areas could classify mostly into mildly corrosive and less corrosive groups to the buried galvanized steel and cast-iron pipes. Furthermore, a new probabilistic corrosion failure model is proposed for the study of the soil corrosivity level more precisely based on sub-corrosion groups by considering the experimental data of six soil factors. Present findings would be insightful for corrosion mapping of soil lands to study the underground pipeline works in the future.