The Science and Technology of Cathodic Protection
Since Sir Humphry Davy described the phenomenon of cathodic protection in 1824, cathodic protection technology has become a standard method for protecting engineering structures from corrosion. However, in engineering practice the protectiveness of cathodic protection can be impaired under some complex and dynamically changing environmental conditions. Examples include steel pipelines buried in inhomogeneous soil under the effects of seasonal changes in soil moisture; cathodic shielding under disbonded coatings; and fluctuating stray currents. These complex environmental variables create major uncertainties in existing cathodic protection criteria and industry standards; and for this reason cathodic protection is considered in industry to be an ‘art’ rather than ‘science’. Over the recent decades significant efforts have been made to achieve an unambiguous understanding of the effects of these environmental variables on cathodic protection efficiency. This present collection of articles documents some recent progresses made in this field. For instance, articles by Ormellese et al., by Hassanein et al. and by Huo and Tan report progresses in understanding the effects of AC and DC electrical interferences on cathodic protection efficiency. Articles by Yan et al. and by Kuang and Cheng report findings about the effects of coating disbondment and cathodic protection shielding on steel pipeline corrosion. Articles by Lambert et al., by Quej-Aké et al. by Broomfield, and by Varela et al., report and review progresses in corrosion survey and characterisation methods. On the other hand, the article by Batt et al. discusses hydrogen embrittlement of cathodically protected high strength steels in sea water and seabed sediment. Improved understanding of these effects on cathodic protection would facilitate more efficient and reliable application of the technology in complex and variable environments.