Section 5 Cathodic protection in tanks

5.1.1 Impressed current cathodic protection systems are not to be fitted in any tank.

5.2.1 Particular attention is to be given to the locations of anodes in tanks that can contain explosive or other inflammable vapour, both in relation to the structural arrangements and openings of the tanks.

5.2.2 Aluminium and aluminium alloy anodes are permitted in tanks that may contain explosive or flammable vapour, or in ballast tanks adjacent to tanks that may contain explosive or flammable vapour, but only at locations where the potential energy of the anode does not exceed 275 J (28 kgf/m). The weight of the anode is to be taken as the weight at the time of installation, including any inserts and fitting devices. The height is to be taken as the distance from the bottom of the tank to the centre of the anode but exception to this may be given where the anodes are located on wide horizontal surfaces from which they cannot fall.

5.2.3 Aluminium anodes are not to be located under tank hatches or other openings unless protected by adjacent structure.

5.2.4 Magnesium or magnesium alloy anodes are permitted only in tanks intended solely for water ballast, in which case adequate venting must be provided.

5.2.5 Anodes fitted internally should preferably be attached to stiffeners, or aligned in way of stiffeners on plane bulkhead plating. Where they are welded to asymmetrical stiffeners, they are to be connected to the web with the welding at least 25 mm away from the edge of the web.

5.2.6 In the case of stiffeners or girders with symmetrical face plates, the connection may be made to the web or to the centreline of the mild steel face-plate but well clear of the free edges. Where higher tensile steel face-plates are fitted the anodes are to be attached to the webs.

5.2.7 Anodes are not to be attached directly to the shell plating of main hulls, columns or primary bracings.

5.2.8 For guidance on the design of sacrificial anode systems in tanks, see Pt 8, Ch 4, 2 Protection of tanks.