Coupled Effect of Soil’s Acidity and Saturation on Pitting Corrosion of Buried Cast Iron

Abstract This paper presents the results produced from long-term tests designed to investigate the key factors affecting the external corrosion of cast iron pipes buried in clayey soil. The coupled effect of varying acidity (pH) and saturation (moisture content) of soil on the corrosion of cast iron buried in soil, including pitting corrosion, is thoroughly examined. Based on the observations and analysis of the test results, it is found that the coupled effect of high acidity (2.5 pH) and high saturation (80 %) of soil could create an accelerating environment for corrosion in the short term. In addition, the coupled effect of low acidity (5 pH) and high saturation (80 %) of soil could lead to a high corrosion rate for cast iron buried in the soil in the longer term. An empirical model for predicting pitting corrosion was also developed. The findings of this paper can have widespread applications, including corrosion protection and the development of models for the prediction of the remaining safe life of pipelines buried in corrosive soils.