Corrosion is the degradation of a metal as a result of a reaction with its environment, affecting almost all metals. The cost of corrosion for most developed European countries is assumed to be approximately 4–5% of the gross national product, suggesting it is an important and real hazard to critical infrastructure.
The predominant form of soil corrosion is electrochemical, resulting in the formation of corrosion pits. Soil environments have generally good electrolytic properties which are essential for the redox (oxidation-reduction) reactions that take place during corrosion, whereby metallic substrates are converted into oxides, hydroxides and aqueous salts within a cathode-anode system.
The complexity and heterogeneous dynamics of soil environments means that soil influenced corrosion is a complicated and not entirely understood phenomenon. A number of soil properties that are thought to contribute to soil corrosivity have been critically reviewed within this report.
The impacts of soil corrosion on critical infrastructure in the UK have been considered. It appears that within the literature most corrosion studies have been instigated, as a need by the gas and water sectors, and a lesser extent to the highways sector. The electricity and telecommunications sectors appear to be little affected by subsurface corrosional processes as cable design has often mitigated this risk and there is little published knowledge stating the contrary. Electricity pylons have been subject to corrosional processes, however the use of cathodic protection has often greatly reduced this risk over recent decades.