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Effective use of anti-fouling paints in marine environment

The shipping industry recognizes environmental protection as one of its highest priorities and that every effort should be made to conserve and protect the environment from marine, atmospheric and other forms of pollution. To prevent the marine ecosystem, the antifouling system was introduced. It is an application of the surface treatment and coatings, paint or device primarily used on a ship to control or to prevent the attachment of unwanted organisms. The smoother a ship's hull, the more efficiently she moves through the water. Antifouling paint is thus useful when applied in the hull. It prevents the build-up of marine growth, which would otherwise reduce the ship's speed and increase fuel consumption. Keeping the hull free of marine growth with one or more coats of quality antifouling paint is, therefore, a top priority for ship owners.

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However it has been proved that certain types of anti-fouling paints that include tri-butyl-tin (TBT) compounds can create adverse impacts on both the marine environment as well as to human health. These paints slowly leach out organotin compounds which act as biocides against individual marine organisms. As a result, the IMO has adopted the International Convention on the Control of Harmful Anti-Fouling Systems on Ships (2001). This Convention, which came into force in September 2008, prohibits ship owners using any TBT compound paints. All coatings on existing vessels were either removed or applied with an overcoating of another specialized paint. In the latter case, the topcoat was acted as a barrier to the compounds leaching from the underlying non-compliant antifouling system.

Vessels will, therefore, needed proof of compliance and essentially, which was in the form of an International Anti-Fouling System Certificate. These certificates are issued by the Flag Administration or organization duly authorized by it. Besides, the Flag Administration now requires a Declaration signed by the Owner/Manager stating that the coating is compliant with the Convention along with the types of coating and date of application.

Since the salt-laden marine environment poses a severe threat to the durability of steel hull structures, proper application of marine coatings is an essential element of a ship's planned maintenance program. Self-polishing antifouling coatings are designed to wear down smoothly while maintaining a bio-active interface between the coating and water. The coating protects against marine growth while minimizing hull resistance. The need for fuel-saving and low emission coatings has driven the growth of marine coatings over the years. This paint type releases biocide at a nearly constant rate throughout its life. The diffusion of the biocide on hull surfaces is primarily due to a chemical reaction between the paint and seawater. The self-polishing mechanism of an antifouling paint film ensures a consistent renewal of paint film and release of biocide on the surface to prevent settlement and attachment of biofouling.

The self-polishing activity is very dependent on the speed and activities of the vessels. Based on various studies, the polishing rate of antifouling paint reduces almost by half when it is stationary as compared to when the vessel travels at 14 knots. Hence, the duration of the vessel staying stationary will enable the colonizing of micro- and macrofouling. Biofouling consists of two main components: microfouling and macrofouling. Microfouling refers to the formation of biofilm and adhesion to the surface, and macrofouling refers to the attachment of organisms such as barnacles, diatoms, and seaweed to produce a fouling community. The growing bacteria and the chemicals they secrete makeup micro fouling also referred to as 'slime,' which develops within hours of an object's immersion in water. Within a few days, macrofouling develops as unicellular eukaryotes, such as protozoa and diatoms. It colonizes the surface. Multicellular eukaryotes begin colonizing the surface within several weeks and include settlement of meroplankton larvae and algal spores.

The marine environment is harsh in terms of corrosion and biofouling. Biofouling generates huge operational losses for the shipping Industry. A high degree of fouling on the ship's hull significantly increases drag, reducing the overall hydrodynamic performance of the vessel and increasing the fuel consumption. Due to these reasons, it is in the best interest of the ship owners to use high-performance coatings that prevent corrosion and antifouling growth on the ship's hull.

Reduced fuel consumption and increasingly stringent environmental regulations have prompted the development of new antifouling technologies. Marine coatings manufacturers are generally cautious in adopting new technologies. However, increasingly stringent environmental legislation, paralleled by customer preference for more eco-friendly products, is pushing innovation in the market.

The need to lower fuel consumption and reduce CO2 emissions has become a strong driving force for paint companies developing new technologically-advanced antifouling coatings for ship's hulls, which reduces fuel consumption. Foul-release technology, which also results in substantial fuel savings, is particularly useful for large cargo ships that consume much fuel. Many companies are investing time and money in developing eco-friendly products such as low friction coatings, metal-free antifouling coatings, and more. Most recent participants now offer silicone- or fluororesin-based foul-release products.

Growth in the shipbuilding industry in China, Vietnam, and the Philippines is expected to provide large opportunities for players in the marine coatings market during the forecast period.

Our articles are based on various shipboard activities, prevention of pollution, safe operation & maintenance procedure. We welcome any feedback from our visitors.

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