What is AntiFouling Paint ? July 21, 2007
Posted by admin in : Antifouling, Marine Paints , trackback
Antifouling paints are paints that we apply on the underwater hulls of ships and boats. As the name suggests, it prevents fouling of the hull of the vessel. Antifouling paints come in various colours and types. Price can range from $6 per litre to over $120 per litre.
Before we go deeper into antifouling paints, let us first discuss a bit about ‘fouling’ and why it is critical to apply antifouling paints.. Where does fouling occur? Fouling in our context occurs on the underwater surfaces of marine vessels (ships, boats etc), buoys, offshore structures and any other submerged objects. Fouling can occur in both salt water and fresh water. What is fouling? Fouling is the settlement of marine organisms on the surfaces mentioned above. The marine organism can either be of plant origin such as algae and weeds, or can be of animal origin such as barnacles and tubeworms. However, the first resident in a fouling process is usually slime. Slime is a viscous and syrupy bacteriological layer consisting of billions of single-celled organism. Once this layer is allowed to establish, the surface becomes more conducive for other bigger organisms to anchor themselves. Effects of Fouling Damage Fouling causes damage to the structure. For wooden or fiberglass boats, severe fouling can cause irreparable damage to the underwater hull and can ultimately cause leakage and collapse of the hull Danger Fouling reduces the responsiveness of the vessel. This may be critical in harsh storm conditions where changing of direction speedily is extremely important in preventing capsize of the craft.
Fouling also weighs on the vessel, making it sit lower than usual. Drag Fouling causes drag which in turns reduces speed and increases fuel consumption. For oceangoing liners, this increased in fuel consumption can be very significant. When does fouling occur? Fouling occurs the moment the structure or vessel is submerged. Fouling generally happens when the structure is stationary. Since most boats remain static for 90% of their time in the water, underwater hulls make perfect feeding and breeding ground for fouling organisms. Certain marine organism such as goose barnacles can attach and grow even when the vessel is sailing.
Anti-Fouling Paints Antifouling paints have been developed specifically to combat this problem. Any vessel owner would know that fouling can be a very big problem, so much so that anti-fouling painting is the most common painting job carried out. Antifouling paints function by slowly releasing toxins into the lamellar sublayer of the vessel, protecting and preventing settlements of fouling organisms. Generally, the type of toxins used and the way these toxins are released differentiates the various classes of antifouling paints. The most common types of toxins used in antifouling paints are copper and TBT (tributyltin) or a combination of the two. Of the 2, TBT is found to be more effective. TBT antifoulings based on the co-polymer technology allows the controlled released of the toxin into the surface of the hull. This type of antifouling paint is commonly known as the TBT antifoulings (SPC). Its effectiveness in preventing growth under many varied marine conditions made it the antifouling of choice for many years. It also lasts a lot longer than copper-based antifoulings. A full system can last up to 5 years, compared to the 12 -18 months that one can get from a copper-based system. TBT-based antifoulings can also be used on aluminium hulls, where copper cannot be used. However, more than 15 years ago, the negative effect of TBT on the environment became a matter of great concern. Worst felt were species of shellfish and whelk, among others. 
In 2001, the International Maritime Organisation (IMO) called for a ban of sales and application of TBT-based antifoulings by January 2003. At the same time, the IMO also called for the total prohibition on hulls after January 2008. This means that ships could no longer be coated with TBT-based antifoulings after January 2003 and those vessels coated with it has up to January 2008 to have them removed. When the treaty comes into force next year, all vessel owners or captains must carry signed declaration that the hull is compliant. With the ban on TBT, copper has again become the toxin of choice. Research and development meanwhile has also led to newer forms of antifouling paints. International Paint has Teflon in some of their antifouling paints. Teflon has a coefficient of friction that is lower than ice and is the most slippery material in existence. It is this smoothness that reduces settlement of organisms. Other areas of research look into using organic or herbicidal compounds to counter fouling. All these research require a lot of time and money. It will be a long way more before a replacement can be found for copper.
We’ll talk about a few specific examples in future posts. Meanwhile, the following link will introduce 2 TBT-free antifouling products from International Paints. http://www.yachtpaint.com/superyacht/sy/pdf/TBT_Ban_Info.pdf
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