(72n) Electrochemical Reactor Modeling and the Determination of Minimum Operating Parameters for Conductive Paint Antifouling Systems

Protection from fouling organisms (biofouling) is a key function of coatings on marine hydrokinetic (MHK) devices. Accumulation of biomass on devices risks performance degradation and possible failure. Additionally, artificial structures in the marine environment have been shown to encourage settlement of invasive species, necessitating application of mitigation strategies.[1] At the present there are no proven reliable options for prevention of fouling in the marine environment with applications to match device lifetimes expected to be on the order of 10-20 years. Removal, cleaning, and re-application of short-lived antifouling paints is an expensive prospect. Electrified conductive paints held at sufficient electric potential have been shown to be effective in the prevention of marine biofouling, and may be a viable solution for long term antifouling performance[2] . The present work seeks to extend the understanding of performance variables for such coatings. Modeling is used to predict chemical species concentrations in fluid flow over a charged flat plate. Minimum operating conditions required for inhibition of algal growth in filtered seawater are then determined experimentally in a flow cell with applicable geometry to elucidate the mechanism of action.

The mechanism of action has been proposed variously to be direct electron transport[2], electromagnetic field repulsion[3], and electrochemical reaction[4, 5]. Evidence suggests that electrochemical oxidation of chloride and bromide present in seawater produces strong oxidizing agents which sanitize the positively charged anodic surface. The negatively charged cathodic surface is likely driving the hydrogen evolution reaction, which increases the local pH to intolerable levels for marine fouling organisms. Comparison of the experimentally determined minimum potential needed for biofouling protection with predicted equilibrium potentials for each reaction and Tafel plots in filtered seawater support this hypothesis.

[1] L. H. Hedge and E. L. Johnston, "Propagule pressure determines recruitment from a commercial shipping pier," Biofouling, vol. 28, pp. 73-85, 2012/01/01 2012.

[2] T. Matsunaga, T. Nakayama, H. Wake, M. Takahashi, M. Okochi, and N. Nakamura, "Prevention of marine biofouling using a conductive paint electrode,"Biotechnol. Bioeng., vol. 59, pp. 374-378, // 1998.

[3] T. Nakayama, H. Wake, K. Ozawa, N. Nakamura, and T. Matsunaga, "Electrochemical prevention of marine biofouling on a novel titanium-nitride-coated plate formed by radio-frequency arc spraying,"Appl. Microbiol. Biotechnol., vol. 50, pp. 502-508, // 1998.

[4] R. E. Perez-Roa, M. A. Anderson, D. Rittschof, C. G. Hunt, and D. R. Noguera, "Involvement of reactive oxygen species in the electrochemical inhibition of barnacle (Amphibalanus amphitrite) settlement," Biofouling, vol. 25, pp. 563-71, // 2009.

[5] J.-R. Huang, W.-T. Lin, R. Huang, C.-Y. Lin, and J.-K. Wu, "Marine biofouling inhibition by polyurethane conductive coatings used for fishing net," J. Coat. Technol. Res., vol. 7, pp. 111-117, // 2010.

[6] Paint and Coating Testing Manual : 15th edition of the Gardner-Sward handbook: ASTM International, 2012.