What Are Anti-fouling Paints?

Anti-fouling paints applied to the bottom of a boat hull prevent the growth of aquatic and marine vegetation and organisms. This growth on the bottom of a boat can slow the boat’s moving speed, drastically reduce fuel-efficiency and cause serious, lasting damage to the boat’s hull like fiberglass blistering.

Anti-fouling paints come in a wide variety of formulas, styles and colors for all types of boats from large sailing vessels to fast-moving motor yachts and smaller, frequently trailered boats.

Many anti-fouling bottom paints are ablative, meaning that they constantly leach an active biocide into the water. The paint has a soft texture that rubs off easily when touched. This constant leaching means that the paint eventually runs through it’s life-cycle, requiring a new application to prevent bottom fouling. Ablative paints are most suitable for slow moving boats or boats infrequently used as the friction of moving water can increase ablating, decreasing the paint’s effective life.

For fast, frequently used or trailered boats, harder epoxy bottom paint formulas are available which are more durable against the friction of moving water and sliding on and off trailer bunks. Special bottom paint formulations are also available for freshwater applications, aluminum hulls and underwater metal components like propellers and rudders.

Commonly, bottom paints dissipate metals like copper to prevent fouling plants and organisms from adhering to the boat’s hull. Copper bottom paints are actually an extension of one of the earliest methods of deterring the growth of these life-forms on ship hulls.

Copper sheets were applied to the hulls of ships for centuries before the advent of anti-fouling bottom paint, a more convenient and inexpensive way of achieving the protection of copper. The active biocide in copper-based bottom paints, cuprous oxide, is still the most common biocide found in the hundreds of bottom paint products available on the market today.

anti-fouling paints

Anti-fouling Paints

Although cuprous oxide is incredibly effective and within the price range of most boaters as an anti-fouling option, concerns about its harmful effects on the environment in addition to the safety of the persons applying it have led to innovative new formulas that prevent bottom fouling while posing less danger to people and the environment.

The copper leached into waterways can contribute to heavy-metal poisoning of animals and humans who consume fish from those bodies of water.

When proper protective gear is not worn while applying bottom paint, copper-based ablative paints can leach through human skin posing serious health risks. One new, less harmful biocide available is cuprous thiocyanate, or white copper. An additional benefit of this biocide is that it allows for more vibrant paint colors.

Organic biocides are also becoming available to boaters. These anti-fouling bottom paints feature non-metal active ingredients, but tend to be more expensive than paints with metal biocides.

As the future of copper-based bottom paints remains uncertain due to increasing legislative efforts to ban it’s use in some U.S. states and other countries around the world, boaters should familiarize themselves with alternatives to traditional copper-based anti-fouling bottom paints.

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