What Is Anti-Fouling Paint?

Anti-fouling paint is used to paint the underwater area of a boat, buoy or ship. Typically manufactured with a specific toxin embedded into the paint, the anti-fouling paint prevents barnacles, slime and other matter from growing on the underwater surface. The length of time for which the anti-fouling paint is functional is dependent on many things, including the quality and price of the paint, with the more expensive paints typically lasting much longer than lesser-priced paint.

Fouling is the act of biological matter growing on the bottom of a ship or boat as well as other underwater surfaces. If left to grow uncontrolled, the growths could destroy a fiberglass boat hull. Other effects of this biologic growth are reduced fuel economy, poor handling and excess weight, which results in the vessel having a lower resting position in the water.

By covering the hull with anti-fouling paint, the growth can be deterred for up to 12 years. In order to properly protect a ship's hull with anti-fouling paint, the vessel must be dry-docked and scraped clean of all existing biologic growth. Barnacles, crustaceans and grass-like growth must all be scraped, ground and chiseled clear of the hull. The hull is then allowed to dry before being covered in paint.

While earlier anti-fouling paint contained chemicals in the form of tributyltin (TBT) and copper, the TBT was banned and subsequent mixtures contained only the copper. Copper has been used for decades to cover the bottom of ships. In the warm waters of the tropics, the copper-clad bottom of wooden sailing ships was used to prevent the growth of tropical grasses from covering the bottom of the ships. The growth would make the ships very sluggish and less responsive to the rudder. This could cause problems when the ship encountered rough seas, with the lack of response hindering emergency maneuvers from the bridge.

Modern anti-fouling paint contains Teflon®. The Teflon® is a slippery material and aids in the prevention of any organic growth being able to cling onto the hull long enough to take root. Of all of the types of painting and restorative processes, anti-fouling paint is the most common type of painting and is repeated on a regular schedule on most vessels. Buoys are also covered in this type of paint in an effort to prevent the excess weight of biologic growth from weighing the buoy down and eventually pulling it under water.