New antifouling tools

Battling marine growth is a never-ending task for the mariner. A major weapon against fouling was lost a decade ago when the federal Environmental Protection Agency banned tributyltin (TBT) as an active ingredient in antifouling paints because of its highly toxic effects on the marine environment. Forced to look farther afield, marine coating companies have devised new tools in the struggle to maintain a clean hull.

Paint companies switched from TBT to copper compounds as the primary active ingredient to deter barnacles. Now a compound called Irgarol, produced by Ciba Specialty Chemicals, reportedly prevents algae and other plant growth from getting established. This, in turn, improves the ability of copper-based paint to ward off barnacles.

After many decades of searching for the best antifouling ingredient, mariners seem to have hit the jackpot when TBT became widely available. This tin compound does an excellent job of killing off any marine life attempting to hitch a ride on your boat. Unfortunately, it also does a great job of leaching into sea water and affecting other organisms. Studies in France in the late 1970s found that TBT caused malformed oysters and other shellfish. In 1981 The French banned the use of TBT on small vessels. In 1988, the U.S. followed suit.

For marine paint manufacturers, the ban on TBT has meant replacing tin with copper as the active. As a weapon against barnacles, copper works well. “For preventing shellfish growth, copper is going to stop it,” said Bob Koeppl, vice president of marketing for Interlux. “The problem [with copper-based paints] typically is algae and slime.” Copper is not as effective against plant-type growth as it is against barnacles. To better battle slime and algae accumulation on boat hulls, chemical additives are blended into antifouling paint. A promising new chemical is Irgarol from Ciba. When added to copper-based bottom paint, this additive, called a “booster” in the paint business, interferes with photosynthesis, preventing chlorophyll-based plants from getting nourishment. Irgarol inhibits an energy transfer system in which water is split to generate molecular oxygen and electrons. Plants then use the electrons to break down CO2 into organic molecules for nourishment. The result of all this is less CO2 absorption and reduced growth.

According to Ciba, one of the advantages Irgarol is its reversibility. Photosynthetic activity is completely restored when a plant is no longer exposed to Irgarol. The mechanism is also non-cumulative. While metals like tin and copper can accumulate in living tissue, an inhibitor like Irgarol reportedly will not be “stored” to adversely affect an organism or plant later in its life cycle. ”

Irgarol is effective in reducing slime,” Koeppl said, “but not in completely eliminating it. The levels at which it is used are critical. It has to be formulated correctly.”

Both Koeppl and Steve Smith, regional sales manager for Kop-Coat marine coatings (Pettit, Woolsey, Z-Spar) stress that Irgarol makes copper-based paints more effective but it will also raise the cost of a gallon of bottom paint. “It is an expensive element of the paint,” said Smith.

Another, more unusual, antifouling coating called Ginsite is being touted by a company in Plantation, Fla., called Ginsite Materials Inc. A mixture of volcanic ash, mica materials, and petroleum-based resins, Ginsite reportedly has a variety of applications as a both a building material and an antifouling coating.

According to Ginsite Materials president and founder Murray Ginsberg, the patented formulation prevents marine growth. “The growth doesn’t like it.” The company applied Ginsite to a variety of surfaces (wood, metal, Styrofoam) and then left them in salt water for 16 months. Reportedly, none of the samples had any growth on them. Although Ginsite Materials claims the compound is effective as an antifouling coating, the company won’t say what it is about the mixture that marine growth finds objectionable. Of course, static testing programs, in which a sample sits in salt water for a given length of time, don’t always effectively replicate real-world fouling, so how well a material like Ginsite will work when its on your boat isn’t so clear.

Unlike metal-based antifouling paints, Ginsite is reportedly non-toxic. It also is naturally buoyant and thus makes vessels float higher in the water. Ginsite Materials is not yet offering Ginsite in a consumer antifouling product.

So the effort against barnacles, marine plant, and slime continues. Who knows what products marine science will come up with next in this age-old contest.

By Ocean Navigator