This European Standard specifies the structures, metals and surfaces which can be protected against corrosion by the application of internal cathodic protection, the electrolytic solutions and the conditions necessary for the application of internal cathodic protection and gives guidance on the application and operation of an effective internal cathodic protection system. This standard applies to the internal cathodic protection of domestic water heaters, hot and cold water tanks, circulating water pipes, condensers, heat exchangers and, generally speaking, to every structure containing an electrolytic solution that it is technically possible to cathodically protect. This standard applies to metallic structures which contain stored or circulating water, which can be stagnant or renewed, cold or hot, drinking water or industrial water and also to aqueous suspension. NOTE Electrolytic solutions are assumed to have a conductivity > 10 -3 Siemens m -1 , and a pH > 4,5. Where the pH < 5,5 or the conductivity less than10 -2 Siemens m -1 see 5.4 and 6.9.2.2. This standard is applicable to metallic structures made from the following on their own or with others: -- iron and low alloy steel; -- galvanised steel; -- copper and copper alloys; -- lead; -- tin; -- stainless steels; -- aluminium and zinc; -- titanium. This standard is applicable to the cathodic protection of uncoated metals, and of metals already coated with low or high insulation resistance coatings.