A laboratory investigation using a specially designed circulating test rig was carried out to study the effectiveness of achieving complete cathodic protection of UNS C71500 heat exchanger tubes in seawater applications. Results indicated that the galvanic current distribution covered the entire 6m length of the tube. The presence of sulphide ions as pollutants in seawater shifted the galvanic potentials of the tubes to more active potentials and prevented the formation of protective films that
normally form. Keywords: Sacrificial Protection, Galvanic Coupling, Heat Exchanger, Carbon Steel, UNS C71500 Alloy Tubes, Seawater and Sulfide Ions Pollutants