Advanced Technology and Manufacturing Institute (ATAMI)

Prevention of marine biofouling is vital to the survivability and performance of ships, buoys, and wave energy devices. Coatings that contain metal biocides are currently used to prevent marine biofouling. These coatings have a limited lifetime and are under environmental scrutiny. As a result, it is necessary to research and develop alternative antifouling methods. One promising alternative is the electrochemical generation of oxidized chemical species. Graphite-polyurethane thin film electrodes were prepared with <20 um synthetic graphite powder mixed with a polyurethane coating. Up to 89 % sheet resistance uniformity was achieved. Open seawater tank experiments, conducted at Hatfield Marine Science Center, with 55 wt% graphite-urethane electrodes on fiberglass substrates were found to inhibit fouling when a constant potential of 1.5 V, 1.2 V, 1.1 V, or -1.5 V versus Ag/AgCl in seawater was applied. Electrodes held at extreme potentials ( -1.5 V and 1.5 V) suffered damage after two weeks of use while the others showed no damage. A 22" long thin film electrode held at 1.1 V was unable to prevent fouling 10" from the electric power contact point, indicating that the local surface potential dropped below a threshold necessary to prevent fouling. It was also found that steel and aluminum substrates were unsuitable as a small scratch in the film electrode exposes the metal to rapid oxidation. Because electrode voltage is vital to its own survivability and antifouling efficacy, voltage profiling experiments were conducted in 3.5 wt % solution of NaCl with 67 ppm Br- from NaBr. A MATLAB program was created to fit model parameters to the experimental results and yielded R² values better than 0.99. Mass transport effects on total current and voltage profile were insignificant for 43 wt % test panels. Both 43 and 55 wt % test panels yielded similar voltage profiles but differed in total current magnitudes.