Cupric tannate: a new pigment for biofouling control

G. BLUSTEIN, B. DEL AMO, M. GARCÍA, M. STUPAK, M. PÉREZ

Badajoz, España

Congreso; 1st International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld-2005). Badajoz, España, 15-18 de marzo de 2005.; 2005

CONTROL OF BIOFOULING BY TANNATE-BASED PAINTS G. BLUSTEIN, B. del AMO, M. GARCÍA, M. STUPAK, M. PÉREZ Centro de Investigación y Desarrollo en Tecnología de Pinturas, 52 e/121 y122, La Plata, Argentina Fouling organisms attached to man-made surfaces submerged in seawater constitute a major worldwide technical and economical problem. Biofouling is a complex sequence of events influenced by several chemical, physical and biological processes. A surface that is immersed in the marine environment will be immediately covered by dissolved chemical compounds that absorb to the surface and evolve to a macromolecular film [1]. This is followed by a process of biofouling where the macromolecular film on the surface is colonized by microorganisms, algal spores and invertebrate larvae. Protection against biofouling is essential for efficient service of boats and ships. The most successful techniques have involved coating ship hulls with metal-containing antifouling paints. These paints are usually based on copper or tin compounds that protect against fouling by continuously releasing the toxic compound into the surrounding seawater. Due to recent and imminent restrictions of the use of traditional, toxic antifouling paints there is a growing need for searching new alternative compounds for marine antifouling paints. Tannins are naturally occurring phenolic compounds which precipitate proteins, they are important in industry, food and environmental sciences [2]. It is well known the anticorrosive properties of tannins since fifty years ago due to they were first suggested for the treatment of rusted steel. On the other hand, antifouling properties of tannins were demonstrated using phlorotannins from Sargassum natans on bacteria, hydroids and nematods [3] In contrast, it is very scarce the information about the effect of condensed vegetable tannins (oligomers and polymers of flavan-3-ol-nuclei) and their effect on biofouling larvae. In a previous paper [4] was demonstrated the narcotic effect of chestnut, quebracho and mimosa tannate on Balanus amphitrite in laboratory trials and the antifouling effect of these compounds in the sea. However, because of non-toxic antifouling paints can not as yet be produced on an industrial scale, there is a growing need for the development of alternative formulations that ensure a good performance without polluting the marine ecosystem. The aim of this paper is to develop a new antifouling formulation using compounds of natural origin, i.e. tannates, in combination with a minimum concentration of a known bioactive pigment, i.e. copper. Laboratory assays shown that cupric tannate have a narcotic effect on Balanus amphitrite nauplii. On the other hand, larvae exposed to leachates from paints recovered rapidly when they were transferred to fresh seawater and completed their life cycles. In the field, after 12 months of immersion in Mar del Plata harbour (Argentine), none of the tested painted panels showed macrofouling organisms and the microscopic observation indicated the presence of some diatoms in a very low density. The performance of the formulation was as good as conventional antifouling paints used as controls. A large decrease in copper content in the order of 40 times in relation to conventional cuprous oxide based paints was obtained. This paint produces less marine contamination and allows a considerable decrease in the costs of paint composition. Acknowledgments The authors would like to thank the Comisión de Investigaciones Científicas de la provincia de Buenos Aires (CIC) and the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). References [1] M. Wahl. Mar. Ecol. Progr. Ser., 58 (1989), p.175. [2] K Chung, T.Wong., Ch. Wei, Y. Huang, Y. Lin.Crit. Rev. Food Sci. Nut., 38 (1998), p. 421. [3] J. Sieburth, J. Conover. Nature, 20 (1965), p. 52. [4] M. Stupak, M. García, M. Pérez. International Biodeterioration & Biodegradation, 52 (2003), p. 49.