In-depth | COATINGS
using a rotor apparatus’, Biofouling, 19 (supplement), 27-36. Candries, M and Atlar, M (2005),
‘Experimental investigation of the turbulent boundary layer of surfaces coated with marine antifoulings’, Journal of Fluids Engineering, 127 (2), 219-232. Ekblad T. (2010). “Hydrogel coatings for
Figure 11: Example of the clear beneficial effect of NEXUS X-Tend on the adhesion to aged silicone topcoat in the waterline area.
products and a competitive price structure.
Conclusion As the shipping industry slowly moves towards higher energy efficiency and lower environmental impact, two technologies are emerging as the preferred choice: the biocide-based Silylated Acrylate technology and the fuel-saving Fouling Release technology. In each of these categories there is a wide range of commercial products already available, as we have summarized in this 2-part review. Within each family, all products are described by similar terminology despite having significantly different formulation parameters. With this background, it is very difficult for a ship owner/manager to know which the most cost-efficient products for their fleet are. As onboard performance monitoring tools become more common and reliable, a larger portion of the market will be able to objectively select their preferred choice of Fouling Control product with subsequent benefits to their fuel bills and the environment. Silylated Acrylate-based paints
base their performance on prolonged antifouling activity, keeping the hull free of macrofouling for longer times than other tin-free technologies (e.g. above 60 months). In this respect, the ship owner/operator should measure almost no decrease in performance due to the antifouling paint throughout the entire dry docking period, with any potential mild fouling compensated for by the self-smoothening of the paint (Weinell, 2003). Biocide-free, FR paints are, on the other hand, more prone to light fouling than biocide-based paints, and are likely to accumulate some slime aſter
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long immersion periods, especially if the vessel stays idle for long times and/or its cruising speed is low. As demonstrated by numerous authors, as long as there is a significant portion of the hull which stays fouling free, silicone-based coatings will lead to fuel savings thanks to their well-recognised low friction properties. Hence, the longer a Fouling Release product can delay fouling, the larger the fuel savings. In Figure 4 and Figure 5, we show that not all FR products are equally successful in such a task. Regarding the magnitude of the potential
fuel savings, Figure 1 shows that Fouling Release coatings will lead to fuel savings even in worst case scenario comparisons. State-of-the-art FR formulations show performance levels comparable to that of the best performing biocide-based products for the entire drydocking cycle (e.g. Figure 3), with important savings as a direct consequence. Contrary to the conclusion of Yebra et al. (2004), one can conclude that silicones are already now a commercial reality and that the market is likely to adopt it as customer confidence grows and the products are optimized even further. Year 2010 witnessed the launch of three new tie-coat products facilitating the touch up and repair of silicone vessels and the conversion of antifouling hulls to a Fouling Release system. Two of these products significantly lower the switching costs to this environmentally-friendly technology aiming at lowering the barriers for the technology shiſt. NA
REFERENCES Candries M, Atlar M, Mesbahi E and Pazouki K (2003), ‘The measurement of the drag characteristics of tin-free self-polishing co-polymers and Fouling Release coatings
biomedical and biofouling applications”. Ph.D. Thesis Linköpings Universitet, Sweden. Finlay, J. A.; Callow, M. E.; Ista, L. K.;
Lopez, G. P.; Callow, J. A. Te Influence of Surface Wettability on the Adhesion Strength of Settled Spores of the Green Alga Enteromorpha and the Diatom Amphora.
Integr.Comput. Biol. 2002, 42, 1116-1122. Finnie, A.A., Williams, D.N. (2010).
Paint and Coatings Technology for the control of Marine Fouling. Chapter 13 in Dürr, S., and Tomason, J.C. “Biofouling”. Blackwell Publishing Ltd. Hellio, C., Yebra, D.M. (2009). Advances
in marine antifouling coatings and technologies, Woodhead Publishing Ltd. Cambridge (UK) Schultz M P (2004), ‘Frictional resistance
of antifouling coating systems’, Journal of Fluids Engineering, 126, 1039-1047. Thomason, J.C. (2010). Fouling on
shipping: data-mining the world’s largest antifouling archive. Chapter 14 in Dürr, S., and Tomason, J.C. “Biofouling”. Blackwell Publishing Ltd. Torlaksen, P., Yebra, D.M., Català, P.
Hydrogel-Based Tird Generation Fouling Release Coatings. Presented at the Eurocoat International Exhibition and Congress 2009. Presentation awarded with the” Golden Coat Award” to the best technical communication of a product. Weinel l, C.E. , Olsen, K.N. ,
Christoffersen, M.W., Kiil, S. (2003). Experimental Study of Drag Resistance Using a Laboratory Scale Rotary Set-up. Biofouling, Vol. 19 (Supplement) pp. 45-51 Westergaard, C.H. (2008). Comparison
of Fouling Control Coating Performance to Ship Propulsion Efficiency. Hempel A/S.
http://www.hempel.com/ Yebra, D.M., Kiil, S., Dam-Johansen,
K. (2004). Antifouling Technology: Past, Present and Future Steps Towards Efficient and Environmentally Friendly Antifouling Coatings. Progress in Organic Coatings, 50, 70-104.
The Naval Architect January 2011
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