This European Standard covers the general principles of cathodic protection including the criteria for protection, environmental and design considerations and secondary effects of cathodic protection and is intended as an introduction to other European Standards in the general series "Cathodic Protection of Steel Structures in Sea Water". This European Standard provides a link between the theoretical aspects and the practical applications of cathodic protection as contained in the European Standards: prEN 12474:1997, Cathodic protection for submarine pipelines. EN 12495:2000, Cathodic protection for fixed steel offshore structures. prEN 12496:1997, Galvanic anodes for cathodic protection in sea water and saline mud. prEN 13173:1998, Cathodic protection for steel offshore floating structures. This group of European Standards does not cover cathodic protection of steel in concrete whether immersed or atmospherically exposed. These aspects are covered by prEN 12696-1:1997 and prEN 12696-2.