antifouling paint prevents biofouling

Improve your vessel’s efficiency with antifouling paint

By volume, 80% of global trade is conducted on our oceans. Our maritime industry is becoming greater by the day, as is our dependence on the vessels that work so hard to achieve it. Biofouling is the growth of microorganisms, plants, algae, or animals that build up on the underwater sections of vessels. This build up decreases the durability and efficiency of a vessel. Antifouling paint works to prevent biofouling, protecting your vessel and your pocket.

This article will outline the specific benefits of antifouling paint, describe the variety of antifouling coatings available, and take a look at the ever-changing regulations regarding biocides. We will also look at the companies that provide antifouling paint products, and where to find them in the US.


Antifouling paint protects the environment and benefits your vessel

The sheer volume of international trade and travel conducted on our seas and rivers shows our reliance on these waterways for much of our day to day life. The possibly harmful effects of this traffic on our marine environment cannot be overlooked, and this is driving the demand for effective, low cost, low impact antifouling coatings as part of a vessel’s complete coating system.

Not protecting with antifouling paint can lead to costly repairs

Not protecting with antifouling paint can lead to costly repairs

Antifouling paint:

  • Lowers fuel consumption
  • Increases the maximum speed of a vessel
  • Increases a ship’s durability
  • Decreases the risk of transferring harmful organisms into foreign waters
  • Protects against damaging marine growth

Pick the best antifouling paint type for your boat or ship

Traditionally, antifouling paints work through the action of a biocide – a chemical substance intended to destroy, deter, or render harmless, or exert a controlling effect on any harmful organism by chemical or biological means. The current biocide used in most antifouling paints is copper, with 90% of antifoul paints using copper or its oxide as their active ingredient. However there is a trend away from biocides, and new products are emerging on the market which use different properties to fight biofouling.

Biocidal antifouling paint – the traditional coating

The mechanism by which biocidal antifouling paints leach biocides into the surrounding water varies depending on the coating type. Pairing the right delivery system with the substrate, environment, and use of the vessel is vitally important for the correct functioning of the coating. The two main categories of traditional biocidal antifouling paint are:

  1. Hard film antifouling coating
    The delivery mechanism for these types of antifouling paint is called ‘contact leaching’. The coating is packed with biocide, and contact with water causes these biocides to leach out. As a result, the antifouling protection is not constant – it starts out high, then wanes as the biocides leach away and all that remains is the hard paint film. These coatings also lose their antifouling ability if kept out of the water, so they cannot be hauled and relaunched without repainting.
  2. Eroding antifouling paint
    As the name suggests, this coating uses erosion to deliver biocides.  This can be caused by the friction of the water passing over the hull, or by a chemical reaction which is localized at the surface of the coating. The biocides are released in a controlled manner, which provides longer and more consistent biofoul protection. Unlike hard film antifouling, boats painted with eroding antifoul can be hauled and relaunched without repainting, since the biocides are chemically bound to the paint and are only active in water.

Foul release coating and other alternatives

Recent developments and the global trend towards sustainability and “green” coatings is driving the study of alternative antifouling methods which do not require the use of a biocide. These include experimental surfaces such as Teflon or silicone coated, hydrophobic, and textured hulls which may prevent the biofouling from growing.

Foul release coatings include silicone elastomers, Teflon-based coating and fluoropolymer coatings, ceramic coatings, and wax coatings. These coatings are also known as ‘foul release’ coatings because the mechanism does not prevent biofouling from settling, but instead the slipperiness prevents it from attaching. The action of the vessel moving through the water is enough to detach biofouling from its tenuous hold.

Another type of antifouling measure is biomimetic coatings. The name comes from the Greek for “life imitating”, and these coatings look to the natural world for inspiration. Coatings that imitate the closely scaled skin of a shark, flocked surfaces that resemble plants, or hydrophobic coatings based on the water-repelling surfaces of the lily pad are all biomimetic coatings.


Choose the best antifouling paint by answering the following questions

Ultimately, the choice of antifouling paint comes down to the best option for the vessel’s substrate, the environment, and the intended use of the vessel. All factors need to be considered to ensure a successful coating. In order to determine which coating is best for your vessel, these are some of the questions you should be asking:

  • What are the costs related to the coating?
    How much does the paint cost? Does the coating lead to greater fuel efficiency? What surface preparation is required? How often will it require repainting, and what cleaning procedures will be required? Prices per gallon is not an adequate representation of price when it comes to antifouling, there are many cost factors at work.
  • What is the lifespan of the coating?
    Not all coatings have the same lifespan, especially under differing conditions. Some will protect for 3-5 years, others for the vessel’s lifetime.
  • How abrasion resistant is the coating?
    The abrasion resistance is relevant for racing vessels, vessels on trade routes that might encounter ice, bumps, or scrapes, as well as ships that require polishing. Highly abrasion resistant paints include the hard film coatings, Teflon, and ceramic coatings.
  • Is the coating suitable for the intended lay-up times, time in port, and water conditions?
    Hard antifouling paints do not maintain their antifouling properties while hauled, where eroding coatings do. Foul release coatings require the ship to move at a certain pace (about 25-30 knots) for the best results, so long times in port or lay-up periods would prevent it from functioning effectively. Mooring conditions in warm coastal waters where marine organisms are densest poses an additional biofouling threat, however many ports are now banning copper biocide to combat rising contamination levels.
  • Where, and how frequently, will the coating and hull need cleaning?
    Can the coating be cleaned without damaging it? Will underwater cleaning risk environmental damage? Downtime from dry-docking and regulations in certain ports preventing underwater cleaning may be factors you need to consider.
  • Are there any regulation changes which may affect the suitability of the coating?
    After the banning of TBT, marine authorities have been wary of biocides in general. Though copper is currently the most common antifouling active ingredient, and it is not likely to go anywhere anytime soon, the antifouling industry is broadening. Biocide-free options are becoming more common and better-performing as companies within the industry move away from biocides.

Antifouling paint regulations in the US – what you need to know

Despite being roughly 1,000 times safer than the tin-based biocides (which were banned twenty years ago), copper is still a concern for the environment. The Clean Water Act standard for copper is 3.1μg/L in marine waters, but in many marinas or poorly flushed basins the copper concentration exceeds this.

Studies have shown that a high concentration of biocides in an environment can have a serious effect on the growth, development, and reproduction of mussels, oysters, scallops, sea urchins, and crustaceans.

The tide appears to be turning against copper. Washington state has enacted a ban for recreational boats on antifouling paints that contain more than 0.5% copper (effective January 1, 2020), and it is illegal to perform underwater cleaning of hulls with eroding antifouling coatings. California and the EPA are both conducting studies into the polluting danger posed by copper, and how to reduce it.

In light of this, coatings manufacturers have been working to create copper-free antifouling coatings to be ready when the legislation changes. New coatings include biocide-free paints such as non-stick surface and ceramic hard coatings.


Antifouling/foul release coatings manufacturers and products in the US

There are multiple bottom paint brands available in the USA. The best choice of paint is the one appropriate for your boat material (fiberglass, metal or wood) as well as the environment in which you keep your boat (salt water or fresh). If you take your boat in both salt and fresh waters, use the antifouling paint for the environment in which your boat spends the most time. Brands available include Rust-Oleum, West Marine, Sea Hawk, Interlux (AkzoNobel) and Pettit. Price varies across products, but with the range available it is possible to find exactly what you are looking for. Many products are not available for retail markets, and need to be applied by professionals and shipyards. It is always best to consult with professionals when choosing an antifouling coating. Below is a table outlining some of the products available.

If you would like more information, our experts are here to help. Just get in touch and we will connect you with one of our coating partners to secure a quote for your project. You can do this  through our contact form by clicking the “Request a Quote” button at the bottom of this article. We will help you find the right coating solution for your needs.

Antifouling paint brandProduct
West MarineBottomShield Antifouling Paint
Pettit PaintBlack Widow Bottom Paint
InterluxACT Ablative Antifouling Paint
Sea HawkCukote Antifouling Paint
Z-SparBottomPro Gold
OceanmaxPropspeed Clear Coat

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