When it comes to antifouling, the many variables involved are enough to cause even the most dedicated owner to throw up his or her hands and just go with whatever the boatyard recommends. And the situation is only that much more complicated if you’re looking for an eco-friendly way to keep critters from attaching themselves to your hull.
First a little history: back in the bad-old days, tin-based paint was the antifouling of choice, for the simple fact that it worked well. However, in the late 1980s the federal government outlawed its use because of concerns it was poisoning the environment. As a result, copper—though more expensive—became the barnacle-repelling agent of choice, although it, too, has now come under scrutiny for its environmental impact. (Thus far only Washington State has imposed any kind of ban—scheduled to take effect in 2020—but California may someday take action as well.)
Whether you agree or disagree that metal-based antifouling is a problem (there are many who argue recreational antifouling represents a tiny fraction of the metal being dumped into U.S. waters) the antifouling industry has been working hard to find non-metallic alternatives—or at least create paints containing as little metal as possible.
Beyond that, when discussing antifouling paints, it’s important to understand that there are various strategies for “repelling boarders,” so to speak.
One is to use a “hard” paint, which dries into a film containing a biocide that leaches out over time as the boat sits in the water. Typically formulated with harder resins, like epoxy, these antifoulings are tough enough to withstand multiple scrubbings, which makes them well suited for raceboats, where a super-smooth bottom is critical.
On the down side, because the biocides in these paints oxidize when exposed to air and thereby lose effectiveness, they are strictly single-season solutions for those up north who store their boats on the hard each winter. (For boats that spend the entire year in the water, 15-17 months is typically the maximum they remain effective.) They also become progressively less effective as the biocide leaches out and have to be sanded, or stripped away periodically to prevent buildup.
Alternatively, biocides can be bound up in much softer paint that wears away as the boat is used, continually exposing fresh material. This category includes “ablative” paints, which typically employ a single soft resin, and controlled solubility copolymers or controlled depletion polymers with multiple resins to fine-tune wear rates in the interest of maximizing performance.
In either case, because fresh biocide is continually exposed as the paint slowly wears away, these paints are often preferred in especially “foul” waters, like those south of the Mason-Dixon line. They also require lower concentrations of biocide to be effective; don’t need extensive sanding between applications because they wear away on their own; and in some cases can be exposed to air for extended periods and then re-launched without repainting.
On the down side, scrubbing a bottom with an ablative antifouling removes the antifouling along with the barnacles and slime, leaving your hull defenseless. With softer ablatives, in particular, you also need to apply extra thick coatings on the leading edges of your underwater appendages, as the paint will wear away much faster in these areas. More sophisticated multi-polymer formulations are substantially more durable, but you still shouldn’t scrub them with anything overly aggressive, like a stiff brush.
Finally, there are paints that don’t contain any conventional biocides. These are produced by manufacturers who march to the beat of a different drummer, sometimes borrowing concepts from nature to repel shells and slime without resorting to the brute force of poison. More on them later.
At present the leading contender to replace copper is Econea, a biocide manufactured by Janssen PMP that is available in a number of different antifoulings. Examples include Hydrocoat Eco and Ultima Eco from Pettit; Micron CF, and Pacifica Plus from Interlux; CFA Eco from West Marine; and Smart Solution from Sea Hawk.
Econea is similar to the copper in that it is extremely effective at discouraging barnacle larva and other critters from establishing a home on a hull. However, it contains no metals and breaks down quickly into its benign constituent parts. Because it contains no metal, it is noncorrosive and safe for use on metal hulls (in contrast to cuprous oxide coatings, in particular, which are the kiss of death for aluminum hulls). The fact that it is light colored also means paints containing it can be produced in a wide range of bright colors and even white.
On the down side, Econea does nothing to prevent the growth of slime and other marine plants. However, this problem is easily solved by pairing it with a second environmentally benign biocide, like zinc omadine—the same stuff used in dandruff shampoo. In some cases, the anti-slime “booster” is given a fancy name, like the “Biolux” used in Interlux’s Pacifica Plus paint.
The fact that Econea doesn’t leach out of hard paints very well is more problematic. At present it is available only in paints that wear away over time, though Pettit’s Tom Maellaro says the industry is attacking this issue aggressively, and he expects Econea to only become more popular with time.
“I could see a time coming, maybe 10 years from now, where there may no longer be any copper-based paints on the market,” Maellaro says, citing Econea’s effectiveness as a biocide.
Maellaro adds that, thanks to recent advances in copolymer paints, it’s now possible for racers and other sailors who like to scrub their bottoms regularly to have their cake and eat it too when going with higher quality paints like Ultima Eco. As long as you don’t scrub your boat with a stiff brush or Scotch Brite pad (Pettit recommends a soft cloth) your paint can last the entire season.
Interlux marketing manager Jim Seidel agrees, noting that his company’s Micron CF has proven successful in a number of racing programs, including on the Class 40 Bodacious Dream, winner of the 2013 Atlantic Cup.
Beyond that, some of the less conventional approaches to antifouling include everything from creating a super slippery surface that is tough for marine organisms to grab hold of to cultivating a thin layer of slime that repels bigger organisms capable of slowing down your boat.
Florida-based ePaint, for example, uses a combination of zinc omadine and a proprietary “photo-active” formulation that repels hard-shell organisms like barnacles and zebra mussels. The latter uses light energy to combine water and dissolved oxygen to form a thin hydrogen peroxide layer that blankets the hull.
Luritek Inc., on the other hand, employs what it calls “stenopropholicity,” as the basis for a multi-season hard antifouling it calls Eco-Clad Bottom Paint. Once applied, Eco-Clad slowly biodegrades to create a food source for a friendly biofilm that naturally repels any other organisms trying to hitch a free ride. Eco-Clad also employs a tough epoxy resin that makes it tough enough for true multi-season performance.
Then there’s Team McLube’s Hullkote, a citrus-based biodegradable hydrophobic hull polish created with the racing set in mind. Although not an antifouling in the conventional sense of the word, this wipe-on-wipe-off product still does a remarkably good job of keeping critters away for weeks at a time, providing your boat is being actively used.
Originally created to help keep dry-sailed bottoms algae free during longer regattas, Hullkote also did a lap aboard Puma’s Mar Mostro during the 2011-12 Volvo Ocean Race, where it served to keep the boat’s bottom clean during the event’s multiple legs. As an added benefit, any slime that does appear can be easily wiped away with a rag.
Another super-slick product is Interlux’s Intersleek 900, which is used on many top-end race boats. Like Hullkote, Intersleek creates a “low surface energy” that makes it difficult for waterborne organisms to latch on and much easier to wipe off when they do. Again, it’s not an antifouling per se, in that it contains no agents that actively repel weeds and barnacles, but if you are willing to dive on your boat regularly during the season, the result is the same—and you don’t have to use a biocide to get there.
Finally, a case can still be made for copper itself. Again, it is not yet illegal, and as Sea Hawk general manager Jason Revie puts it, it has more than proved itself for centuries.
With this in mind, all the major manufacturers offer copper-based antifoulings engineered to do more with less through carefully tailored resin and release formulations. “There are different polymers and different things you can do, including combinations of different biocides,” Revie says, citing his company’s Biocop TF as an example of this approach.
Along these same lines, Interlux offers a self-polishing product called Micron CSC, and Pettit’s Vivid “bright color antifouling” employs a combination of a zinc-based anti-slime agent and cuprous thiocyanate, a copper compound with less metal than cuprous oxide.
The result is that there are a number of options for those who don’t want to give up copper entirely, but are still interested in doing right by Mother Nature.
And Now for Something Completely Different
Wouldn’t it be great if a boat’s hull could be made intrinsically unattractive to marine growth? In the case of the UK’s Ultrasonic Antifouling (ultrasonic-antifouling.com) one to four transducers—depending on your boat’s LOA—are attached to the inside of the hull to create an “environment of moving water molecules” that makes it impossible for the “cell structures” of various different microorganisms to survive.
SAIL’s Charles J. Doane recently installed an Ultrasonic Antifouling system on his aluminum Tanton 39 cutter Lunacy and has been pleased with the results. Used in conjunction with Pettit’s Vivid Free antifouling, there was still some growth at the end of the year, especially along the trailing edge of the rudder, but not enough to affect performance—not bad given the fouling typical of Portland, Maine.