EVALUATION OF WARSHIP IMPRESSED CURRENT CATHODIC PROTECTION SYSTEMS

It is described how the effectiveness of the cathodic protection afforded by different warship system configurations was assessed using a physical modelling technique in which a one-sixtieth scale model hull was immersed in sea water whose electrical conductivity had been reduced by the same factor. The performance of four- and six-anode systems controlled by a single reference electrode sited amidships was unsatisfactory, particularly in simulated underway conditions. Incorporation of an additional reference electrode at the stern provided a significant improvement in the potential around the hull although there was interference between the two control zones; this can, however, be avoided. An 'all-aft' configuration, employing a single pair of anodes fitted adjacent to the A-brackets and controlled by a single reference electrode at the stern, performed well under the trial conditions. It is concluded that the design of an efficient impressed current cathodic protection system requires optimum positioning of the reference electrode(s) and the associated anodes, which can be determined by physical modelling.