Analysis on Variations in Underwater Electromagnetic Signals of a Surface Ship as Varying Placement of ICCP Anodes

The impressed current cathodic protection (ICCP) is widely used for preventing galvanic corrosion and it strongly influences the underwater electromagnetic signals of a surface ship. For military use, the signals should be reduced to avoid threats such as modern naval weapons triggered by the signals. We analyzed the underwater electric field (UEF) and corrosion related magnetic field (CRM) of a surface ship with four pairs of ICCP anodes using the boundary element method and varying the anodes placement in a longitudinal direction. The currents applied on ICCP anode pairs was optimized to minimize the UEF under corrosion protection of the hull using sequential linear programming at each placement of the anodes. As a result, UEF and CRM decreased as the root mean square of the distances between ICCP anode pairs on the hull decreased, but they were not intimately related to the total amount of the currents from the ICCP anodes under the optimized condition.