Non-biocidal antifouling coatings

 
Research and development of "Hybrid organic-inorganic'' nanocomposites, which are composed of organic and inorganic components combined over length scales ranging from a few Angstroms to a few tens of nanometres, has grown considerably since the early 1980's. This growth is due to the development of soft inorganic chemistry processes, especially sol-gel processes. A further expansion in this area is the development of functional sol-gel systems, addressing applications such as self-healing, self-cleaning, anti-icing. A more recent application of the sol-gel system is that in the area of antifouling. In this presentation we report on the use of naturally occurring living bacterial entities, notably endospores, intended to exploit the mechanisms used by living organisms designed to repel the settlement of fouling organisms [1]. The coating systems are based upon the incorporation of endospores into a silanebased sol-gel system. Two aerobic endospore-forming bacterial types have been studied; Paenibacillus polymyxa and Bacillus licheniformis, each type individually incorporated into a sol-gel matrix. In addition to simple abiotic and biotic coating formulations, additional variant coatings were prepared based upon simultaneous incorporation of bacteria and corrosion inhibitors. Corrosion resistance performance of the coating systems was based upon electrochemical impedance spectroscopy analysis and simple immersion based field trials. Field trials were based in both the UK and Saudi Arabia. Thermal properties of the sol-gel matrix were evaluated using Thermal Gravimetric Analysis. Coating morphology was evaluated using scanning electron microscopy and viability of bacterial strains was assessed using confocal fluorescence microscopy. Water repellency was assessed based upon water contact angle measurements. It was concluded that incorporation of bacteria improved the fouling resistance of the coating and that additional corrosion resistance was seen when both bacteria and corrosion inhibitor was present together in the coating.