Alteration of soil support to cast iron pipelines due to corrosion

This paper describes research into the effects of corroding cast iron pipes on the properties of surrounding clay soil. Accelerated corrosion tests, employing electrokinetics to simulate the galvanic cell that is set up naturally when cast iron comes into contact with clay, have shown that the chemical changes (e.g. pH) are more marked than for cases in which inert electrodes were used. These chemical changes result in both cast iron and clay mineral dissolution, ion migration and the precipitation of reaction products close to and - to a lesser degree - away from the pipe wall. The paper describes a laboratory study of the effects on a pure form of kaolinite after different lengths of electrokinetic treatment and draws conclusions on the potential effects that are likely to be found for old cast iron pipes in clays.