Corrosion behaviour of pipes in soil and in simulated soil solution

Corrosion is a serious concern for asset managers and owners of the buried pipelines. Millions of dollars are spent every year on the repair and maintenance of the existing buried water pipes which were laid underground many decades ago. Recent investigations revealed that the external corrosion can be the root cause of failure for buried cast iron pipelines. Hence, various research works have been reported in the literature to discover the corrosion effect on pipes buried either in real soils or simulated soil solutions. However, the corrosion models developed on the basis of pipes in these two environments are not largely comparable. In the current research, the carefully controlled test program was executed to investigate the corrosion behavior between the pipes buried in soil and simulated soil solution. Firstly, a series of experiments was conducted using cast iron pipe coupons buried in homogenous real soil environments having a constant void ratio, the degree of saturations and pHs. Secondly, cast iron pipe coupons having similar material composition were submerged in simulated soil solution which was created from the corrosive components of the same soil. Results revealed a substantial difference in the metal corrosion rates between the different interaction mediums. The research findings can be helpful to develop a correlation model to compare the corrosion rates of cast iron metals between soil and simulated soil solution mediums. Such models will support more reliable and convenient service life prediction of cast iron pipes when the corrosion experiments are based on simulated soil solutions.