Features March 1, 1999 Issue

Spring Maintenance: Antifouling Tests '99

After the loss of our Foulbottom raft, we started over with 51 new paint samples. Rated for resistance to hard and soft growth, Interlux professionally applied Veridian and the not-yet-available Micron Optima were best.

There are many rites of spring—trees bud, houses are cleaned, young men’s fancies turn and boaters get ready for a new season on the water. Here at PS, spring means wrapping up the past year’s tests of antifouling paints and preparing for next year's test program, a cycle that’s been continuing over the past eight years.

Last year, as constant readers may recall, was a rough one. It was the year that the Foulbottom, the specially constructed raft used for our test bed, parted its mooring chain in a storm and was lost at sea with 36 test panels aboard, effectively terminating our longevity tests. A concurrent test started in Florida did survive, but only provided one season’s worth of data. And another test set up on Lake Champlain (to see how the various paints could cope with zebra mussels and other freshwater growth) was aborted when an assistant sold his boat.

Dismayed but not undaunted, a new, bigger, stronger raft, the Foulbottom II, was built and commissioned. Where last year’s load of 36 panels was pretty much the limit for the old raft, Foulbottom II’s greater capacity allowed us to test more antifoulants. This year, no fewer than 51 different products were tested, including a dozen or more that had been tested in previous years. Starting over this way has both advantages and disadvantages. We’re able to directly compare a large number of products under identical conditions, which makes for a more satisfactory test. On the other hand, it’s going to take a long time to reestablish relative longevity figures.

Unless we’ve miscalculated badly, Foulbottom II should last for many years. She’s held in place by five mushroom anchors and five mooring chains (we’re also running a test on mooring chain corrosion). And so, hopefully, we’re once again set up to develop the type of long-term data provided over the past years.

What’s This All About?
For the benefit of those who haven’t been following this series of reports, PS has conducted (and will continue to conduct) tests to help the boat owner determine which products offer the best and longest-lasting protection against barnacles, mussels, tube worms, algae, slime, grass and seaweed, to mention just a few of the over 2,000 different species of flora and fauna that have been identified on the bottom of boats.

The tests are simple and straightforward. The panels are put in a body of water conducive to marine growth. We’ve concentrated on two aspects of a paint’s performance: How clean will it keep your hull? And, how long will it last? The importance of the first aspect is obvious. A foul bottom costs a lot in terms of speed, fuel economy and—most important—the time and labor involved in scraping it clean. The second aspect—longevity—also is important, not only for the obvious reasons of saving both material and labor, but for the less obvious one of environmental benefit. Any paint on a boat’s bottom will ultimately contribute to environmental pollution because the portion that comes off or dissolves in the water winds up adding unfriendly elements to the water, while frequent prepping and painting generates dust and paint chips that must be disposed of and (to the extent that the paint contains volatile organic compounds, or VOCs) contributes to air pollution. An antifouling treatment that lasts longer is good for both the owner and the environment.

What We Tested
Because many manufacturers offer a variety of products, covering a wide price range, we contacted the ones we could locate, and asked them for recommendations. The list of 51 products on the ratings chart itemizes those selected.

These 51 represent a number of different approaches toward antifouling. While there was a period—between 1960 and 1980—that there was a single effective solution to the problem of fouling, that solution has been suspect since the early 1980s, when it was realized that tributyl tin, the active antifouling ingredient, also killed marine life that wasn’t attached to the boat, such as fish and shellfish. The use of tin as an antifoulant was banned by the EPA in 1989.

The most popular approach to producing an antifouling coating is to incorporate copper or copper oxide in a paint. This theme permits several variations: ablative paints, which soften and slowly slough off with time, constantly exposing a fresh surface to the water (and the underwater critters); and hard-finish modified epoxy paints that don’t wash off, but rather permit enough water to permeate through the coating to dissolve some of the copper. Copper-loaded gelcoats—the three we tested are all based on two-part epoxies—appear to work the same way, but with a slower release of copper. Other biocides have been used in place of copper over the past few years, including zinc oxide and cayenne pepper. The only one represented in the current test is copper thiocyanate (used in Interlux’s Trilux), a relatively inert compound of copper. Bio-release coatings, theoretically slick enough to prevent fouling organisms from getting a solid grip on the hull, are represented by Veridian, a rubbery silicone-based coating that’s proved very effective (and hellaciously expensive) in previous rounds of testing.

Another aspect of bottom paint that is being addressed by the paint manufacturers is the problem of air pollution during application due to the solvents that are used in the paint. To minimize this problem—and to meet state and local regulation on permissible VOC levels—manufacturers are developing more and more water-based antifouling paints. Water-based paints for underwater service may sound odd, but these paints, once dried, are adequately water-resistant and offer many advantages, not the least of which is the ease of cleaning brushes, rollers and the person who does the painting.

The latest trend, at least from a technical viewpoint, is the addition of paint ingredients aimed at reducing soft growth on painted hulls. Two products we tested—Trinidad SR and the not-yet-marketed Micron Optima—claim to reduce soft growth build-up. Our preliminary one-year results are promising.

Another trend, though it doesn’t seem to have any effect upon performance, is the corporate coalescing that’s going on in the marine paint industry. Some years ago, Woolsey, Pettit and Z-Spar became part of Koppers. This year there is a tighter integration of the three, although products are retaining their individual brand names instead of the umbrella name of Kop-Coat. Gloucester, Tarr and Wonson, and KL990 were marketed by Rule Industries until last year, when Nautical Paint, which also manufactures the US Yacht and West Marine lines of bottom paint, acquired them. This year, Interlux acquired Nautical Paint and was, in turn acquired by Azko Nobel, making Azko Nobel the supplier of no fewer than 27 of the products we’re testing.

How We Test
We take fiberglass panels, prep them according to the various paint manufacturers’ recommendations, and then paint one side of each panel with a bottom paint, also according to instructions. In the few cases where products are sold only for professional application, we ship panels to the manufacturers and let them apply the coating.

Panels are then coded and identified by patterns of large-diameter and small-diameter holes drilled in the panel, using a binary numbering system (remember the New Math?). This eliminates the risk of having painted identifying marks wash off or become illegible. To eliminate any unconscious bias a tester might have, codes are assigned by a staffer who isn’t involved in the later performance evaluation.

The panels are attached to racks, which are in turn mounted on the test raft. The raft is anchored with the panels almost completely submerged; periodically, the raft is towed around at a modest speed behind a small powerboat to simulate occasional use on a real vessel.

The panels are generally left in the waters of Greenwich Harbor for what corresponds to a full boating season in Connecticut—May through October. This year, the season was shortened by a month and a half due to the necessity of replacing the Foulbottom and its load of test panels. Greenwich is a fine place for growing marine organisms. Apparently, a combination of shallow water, poor tidal water exchange, a black, mucky bottom and extensive run-off from heavily fertilized lawns all make for a richer harvest of underwater marine life than would normally be expected at this northerly location.

Evaluations in the past have focused almost completely on how well each product resisted hard marine growth. This type of fouling, after all, is the most difficult and labor-intensive to remove. When our testing program started in the early 90s, enough products exhibited early failure to make this the overwhelming ratings factor. More recently, however, most of the products tested do quite well in resisting hard growth, at least for a year or two. Consequently, the emphasis has shifted to longevity of protection, and, starting with this report, to giving more weight to resistance to soft growth—grass, slime and seaweed.

From what we’ve been able to tell, the rate of soft growth can vary tremendously from year to year in any given location. The new, larger test raft has allowed us to start all the products at the same time, eliminating year-to-year variability as a major concern. This capability, of course, will disappear as new products appear.

What We Found
Findings are summarized in the chart on page X. As mentioned earlier, most antifouling paints now do a fine job of keeping off hard growth, at least for the first season.

Any product rated Excellent in dealing with hard growth exhibited no hard growth at all. A Very Good product had a very few barnacles; a Good one had scattered growth over its surface; one rated Fair had widespread, moderately heavy growth. One rated Poor was totally ineffective, or had such poor adhesion that whatever antifouling characteristics it might have were irrelevant. While virtually all the products were rated Excellent for their first year’s performance, this wasn’t due to any shortage of barnacles, because the unpainted rear surfaces of the test panels as well as the untreated polyethylene floats of the Foulbottom II were heavily encrusted.

Soft growth is harder to rate, involving a bit more subjectivity. Excellent means pretty much the same thing as it does for hard growth: virtually no slime, grass or other vegetation. A Very Good rating means that, although there was an appreciable amount of slime, the paint’s color was still easily discernible. Good indicated a heavy coat of slime, but no other growth of vegetation. A rating of Fair was reserved for panels that collected enough flora to show up as distinct shapes. A Poor rating would be earned by a heavy coat of grass or seaweed covering the entire surface, but none of our paints were rated as Poor.

The ratings order is determined by how well a product performed in keeping off hard growth; products with the same hard growth ratings are listed in order of soft-growth performance; products with the same score for both hard and soft growth performance (and in this short test, there are many) are listed alphabetically.

Only two products were rated excellent in both categories, and neither will do the average boat owner any good—at least at this time. Interlux’s Veridian, a thick silicone rubber bio-release product, is currently available only as a professionally applied treatment at the astronomical price of $35 per square foot. Interlux tells us that Veridian may be available as a spray-applied coating in the future, but we suspect that it will still be prohibitively expensive. We’ll keep testing it simply because it demonstrates that a zero-environmental-impact approach is possible.

The other product that produced excellent results in terms of dealing with both hard and soft growth is another Interlux formulation—Micron Optima. It’s not available in the United States at this time. According to Interlux, Micron Optima is awaiting EPA approval, and will be sold as soon as that is obtained. Micron Optima is unusual because it’s a two-component water-based paint that must be mixed immediately before use. This can be a nuisance, as the product’s pot life, when mixed, is too short to let you apply a second coat without mixing up a new batch. Because the quantities to be mixed aren’t equal—a small XX-oz. container must be mixed with a large YY-oz. one—mixing up less than a full batch requires some inconvenient measurement. We’d hope that some provision for mixing up, say, a third of a gallon, will be provided when Micron Optima reaches the market.

The only other product that we know of that’s formulated explicitly for prevention of slime and vegetation is Pettit Trinidad SR, which includes in its formulation a new anti-slime agent called Irgarol, developed by Ciba. While not quite as effective as Optima in our tests, it nevertheless did a creditable job of keeping off slime, earning a Very Good rating in that respect. No fewer than 19 other products also earned the same scores (Excellent for hard growth, Very Good for soft); we’ll have to wait to see how each one lasts.

Of the three copper-loaded epoxy gelcoats we tested, Epcotek excelled, scoring Excellent for hard growth and Very Good for soft growth. Copperpoxy scored Excellent and Fair. Permashield was Very Good for both. While our Permashield panel had a few barnacles, they were very easy to remove.

Freshwater Test
There was neither time nor space to prepare all-new sets of panels for the Florida or freshwater test sites. We decided to restart last year’s aborted freshwater test with the original 36 products. Our tester had purchased a new boat for chartering on Lake Champlain.

At season’s end, we found that all the paints did a good job of keeping zebra mussels off. There were certainly mussels present in the water. Our Man Up North reported extensive growth of the pesky mollusks on the untreated backs of the panels and on the raw edges, as well as at the edges of the holes drilled in the panels for identification.

With two exceptions, all the panels emerged from the test with a coating of slime; untreated areas had extensive vegetation. Veridian was the cleanest, closely followed by Tropikote. Panels treated with these products had a very few patches of slime.

Three other products—ACP50, America’s Cup and Super Shipbottom—appeared to have less of a slime coating than did the others. All the rest were roughly equivalent in terms of blocking soft growth. In no case was slime judged to be a serious problem. In all cases the surface could be cleaned up easily with a pressure washer and no scraping.

We’ll continue our freshwater tests in the coming years, and hope to develop some meaningful longevity data, including the new arrivals to our Connecticut test.

Conclusions/Recommendations
The current round of tests can only be considered a work in progress. First-year results can’t give any indication on product longevity. They do suggest, however, that if you’re in the habit of yearly bottom painting, you have a lot of paints to choose from.

If you’re looking for something that lasts for several years, we must refer you back to our last series of tests that indicated we could get three full seasons of barnacle-free hulls from a number of products: Interlux Veridian, Petit ACP50, U.S. Yacht Ultra CopperKote, Tropikote, and Super Shipbottom.

Veridian and ACP50 were the only ones in this group that we tested for a fourth season; Veridian continued to be Excellent, while ACP50 dropped off to Very Good. It should be noted that ACP50 is an ablative and comes off easily when scrubbed in the water. Several readers, including PS editor-at-large, Nick Nicholson, have complained of this. Ablative paints may be best used for boats that don't move a great deal.

The three copper-loaded epoxy gelcoats—Copperpoxy, Epcotek 2000 and Permashield—continued to provide Very Good performance against hard growth and mediocre protection against soft growth through our fourth and last season of testing.

We will continue—and expand upon—the testing of antifoulants in the years to come.


Contacts- American Marine Coatings, 1445 Northlake Way, Seattle, WA 98103; 206/633-3308. Flexdel Corp., 1969 Rutgers University Blvd., Lakewood, NJ 08701; 732/901-7771. Hi-Tek Chemical Co., 106 Taft Ave., Hempstead, NY 11550; 516/538-0400. Innovative Marine Coatings Inc., 15870 Lake Candlewood, Ft. Myers, FL 33908; 800/466-7144. Interlux Yacht Finishes, 2270 Morris Ave., Union, NJ 07083; 800-INTRLUX. ITW Philadelphia Resins, Box 309, Montgomeryville, PA 18936; 215/855-8450. Nautical Paint Industries, 1999 Elizabeth St., North Brunswick, NJ 08902; 800/432-4333. New England Paint Mfg. Co., 15 Higginson Ave., Central Falls, RI 02863; 401/722-4606. New Nautical Coatings, 2181 34th Way, Largo FL, 33771; 800/528-0997. Petit Paint Co., 36 Pine St., Rockaway, NJ 07866; 800/221-4466. Rappahannock Coatings, 1200 George Wood Dr., Elizabeth City, NC 27909; 252/335-5797. Stargate, 6699 E. Peden Rd., Fort Worth, TX 76179; 817/236-6699. U.S. Paint, 831 South 21st St., St. Louis, MO 63103; 314/621-0525. US Yacht, 1999 Elizabeth St., North Brunswick, NJ 08902; 800/566-5668. Woolsey/Z-Spar Marine Paint, 36 Pine St., Rockaway, NJ 07866; 800/221-4466.

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