In this paper, the influence of mixed-type (impressed-current and sacrificial-anode) cathodic protection on an underwater electromagnetic field was investigated using the boundary element method. The current applied for cathodic protection was reduced by installing sacrificial anodes in the stern region. Also, the potential difference produced by the propeller in the stern region was decreased, due to the effective potential distribution generated by the sacrificial anode. The underwater electromagnetic signature decreased at 18 ℃ and 5 m/s, but not at 6 ℃. The difference in current density produced by the environment influenced the intensity of the electromagnetic field. The dramatic decrease in applied current at 6 ℃ increased the maximum electromagnetic signature. Thus, while the mixed-type cathodic protection effectively reduced the underwater electromagnetic signature, the design of the mixed-type cathodic protection should be optimized based on the environmental conditions, due to the sacrificial anode effect.
Keywords: cathodic protection, electromagnetic field, sacrificial anode, boundary element method, seawater
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