Bio-friendly antifouling paint beats toxic alternatives

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Researchers at Sweden’s Chalmers University have shown that silicone-based, non-biocidal antifouling paints for boats and ships can outperform toxic, copper-based paints.

The black surfaces are coated with biocide-free silicone-based paint, the red surfaces are coated with copper-based paint and the white surfaces have no antifouling treatment.
The black surfaces are coated with biocide-free silicone-based paint, the red surfaces are coated with copper-based paint and the white surfaces have no antifouling treatment. - IVL | Anna-Lisa Wrange

Antifouling paints are applied to marine vessels and structures to deter the growth of subaquatic organisms like barnacles, which can affect performance and integrity. However, the copper-based products that proliferate the market are a well-known ecological threat, as the heavy metal does not degrade and can contaminate marine plants and other organisms. Eco-friendly alternatives are available, but copper-based paints still dominate.

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“Both the shipbuilding industry and the leisure boating sector have one thing in common: they are highly traditional,” said Maria Lagerström, researcher in marine environmental science at Chalmers. “People like to use the products they are used to, and they are also sceptical as to whether non-toxic alternative solutions really work.”

In an effort to try and address this scepticism, the Chalmers team conducted a year-long study at three sites in the Baltic Sea region and the Skagerrak, the strait between the North and Baltic Seas where Norway, Sweden and Denmark come together. When the researchers compared copper-based antifouling paint with silicone-based paint, it was found that the bio-friendly product outperformed its toxic cousin at keeping the fouling at bay. The work – carried out in partnership University of Gothenburg and the Swedish Environmental Institute IVL - is published in Marine Pollution Bulletin.

“This means that we now have a great opportunity to drastically reduce the release of the heavy metal into our sensitive sea,” said Lagerström. “This is the first independent scientific study to show that silicone paint is more effective than copper-based paint in the Baltic Sea region.”

According to the researchers, the work has particularly strong implications for the Baltic region due to the geography of the sea around the Nordics and the Skagerrak, and the abundance of marine traffic that the area is home to.  

“As the Baltic Sea is an inland sea, it takes 25–30 years for the water to be exchanged,” said Lagerström. “This means that the heavy metal remains for a very long time. It is therefore important to be aware of the substances we release.”