Experimental investigation on corrosion effect on mechanical properties of buried cast iron pipes

A review of published literature on the corrosion of metal pipes reveals that current research on corrosion of full-size pipe sections in real soil conditions is highly limited, with almost no research reported on the corrosion effect on degradation of mechanical properties, and fracture toughness in particular, of cast iron pipes buried in real soil. This paper presents a new testing methodology for investigating the corrosion of cast iron pipes in real soil and evaluating its effect on the degradation of both fracture toughness and modulus of rupture in various environments represented by different pH values of soil. Microstructure analyses of pipe specimens before and after corrosion were also conducted to identify possible causes for degradation of mechanical properties, and specimens were compared with exhumed pipes. Both fracture toughness and rupture modulus of pipe specimens decreased with corrosion, and localized corrosion and formation of the graphitized zone in cast iron pipes were the primary causes for degradation of their mechanical properties. The results presented in the paper contribute to the body of knowledge of corrosion in realistic soil and its effect on the mechanical properties of buried pipes.