Quantitative Study of Coupled Effect of Soil Acidity and Saturation on Corrosion and Microstructure of Buried Cast Iron

Corrosive soil has been reported to be a prominent cause of the failure of buried cast iron pipes. Little research has been conducted with a specific focus on the effects of soil acidity and saturation on the corrosion of buried cast iron and subsequent microstructural changes in the corroded cast iron. This paper presents results produced from a comprehensive experimental program designed to determine the coupled effect of soil acidity and saturation on corrosion and subsequent changes in the microstructure of cast iron buried in soil. Relations between corrosion and subsequent microstructural changes in corroded cast iron with affecting factors and time were developed. The study determined that soil with low acidity (pH 5) and high saturation (80%) was the most corrosion-prone environment among the various soil conditions investigated and that corrosion can cause significant changes in the microstructure of cast iron. The significance of these findings is that any changes in the microstructure of cast iron can directly affect the mechanical properties of the corroded cast iron, which are directly related to the service life of corrosion-affected cast iron pipes.