Corrosion induced failure of the ductile iron pipes at micro- and nano-levels

Abstract

Corrosion induced failure of buried ferrous pipelines causes significant economic losses to the world. Many of the existing buried water pipelines are made of ductile iron in most of the developed countries. Literature shows that the research on the corrosion-induced degradation assessments of ductile iron pipelines is limited and mostly deals with the physical deterioration i. e., loss of wall thickness determined by short-term research. This paper addresses this gap and presents a comparatively long-term study on the corrosion and its subsequent effect on the composition and nanomechanical properties of buried ductile iron pipelines in the accelerated corrosive environment. For experimentation, ductile iron specimens were immersed in the acidic simulated soil solution for 365 days. Physical deterioration assessment over the time was carried out in terms of corrosion rates measured at intervals of 180 and 365 days. A significant change in the percentage composition of key elements and phases were quantified. Furthermore, the mechanical properties of the grains were found to be considerably reduced after 365 days of immersion in the acidic environment by the nanoindentation technique. The results revealed an alarming increase of structural degradation at nano scale for some of the grains due to chloride induced localised corrosion. The significance of the current research is its in-depth analysis of the corrosion-induced degradation of ductile iron pipes which enhances the knowledge related to the failure of these pipelines.