Silicone boat paint is both safer and greener for ships

Both cargo ships and luxury yachts are vulnerable to the buildup of algae, barnacles and various other marine organisms as they travel the world’s waters. The aquatic hitchhikers are not just an eyesore – barnacles can compromise the integrity of boats and also slow them down drastically due to resistance to drag. To counter this, manufacturers have long turned to toxic copper-based “antifouling” paints to protect the hulls of large ships, which discourages organisms from growing on the surfaces and often ultimately kills those who manage to to attach.

Unfortunately, the biocides in these paints are the cause of frequent concern from environmentalists because they remain in water systems for decades and harm local ecosystems by poisoning species and their environment. Recently, scientists have shown how an existing alternative to popular copper-based antifouling agents is not only potentially better for the environment, but also appears to be more effective.

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In a joint study published in the Marine Pollution Bulletinresearchers tested biocide-free silicone-based coatings alongside more traditional copper-based paints at three locations in the Baltic Sea region, but found that the silicone kept surfaces cleaner longer than its toxic predecessors.

“We actually left our test panels at one of the test locations. These have now been under the surface for more than two years. We can see that the silicone paint still works well and, more importantly, works better than the copper paint,” said Maria Lagerström, a researcher in marine environmental sciences at Chalmers University, in a public statement.

According to the researchers, an estimated 40 percent of copper imports into the Baltic Sea come from antifouling paints. “Because the Baltic Sea is an inland sea, it takes 25 to 30 years for the water to be exchanged. This means that the heavy metal will last for a very long time,” Lagerström adds. “It is therefore important to be aware of the substances we release.”

Unlike biocidal paints, silicone coating options rely on their smooth surface properties rather than toxic chemicals harmful to marine life. Silicone coats are simply too slippery for most barnacles and algae to develop – not only that, but whatever life forms on hulls eventually falls off as ships move through the water.

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While silicone alternatives have been available for years, the marine industry has been slow to adopt paint standards over biocidal copper. As Chalmers University reports, as of 2014, silicone coatings accounted for only about 10 percent of the market share for marine vessels, with even less employed by recreational craft. “Both shipbuilding and pleasure craft have one thing in common: they are very traditional. People like to use the products they are used to, and they are also skeptical about whether non-toxic alternative solutions really work,” says Lagerström.

The latest research makes it clear that while silicones appear much less toxic than copper-based biocidal paints, they can still be harmful in other ways. The conclusion of the study cites the wide variability in currently available silicone coating products coupled with their relative lack of regulatory oversight of biocidal paints as a cause for concern. Even without biocides, some silicone varieties still show toxic effects from their leachable materials, especially within the first few months of their application. Other silicone fluids, while not necessarily toxic, remain in the marine environment for an extremely long time and thus may pose unseen threats. While the research team still maintains the superiority of silicone coatings over demonstrably harmful copper-based biocidal paints, the study urges future research into these potential issues to ensure the creation of the safest possible products.

Switching to silicone anti-fouling is a great first step towards healthier sea voyages, but far from the only reform needed right now. In addition, ocean routes need to be re-examined to better protect endangered animals, in addition to the changes that must come from international climate change regulations. Last year, advocates also pushed for the development of net-zero overseas shipping lanes to reduce carbon emissions.

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