According to Santiago Arias, head of product sustainability at Hempel, it’s time boat owners were encouraged to explore alternatives when making decisions about hull protection. They need to understand and consider the impact of biocides on the marine environment and look at what else is on offer.

“While biocidal antifouling paints have been traditional choices, there’s now a range of alternatives to choose from,” Arias says. “Upcoming regulations could further support the adoption of environmentally responsible solutions, signalling a positive shift towards more sustainable practices in the marine industry.”

Arias says concern has arisen that biocide releases can lead to adverse effects on non-target organisms, especially in marinas and environmentally pristine areas where pleasure craft (typically less than 24 metres) congregate in large numbers.

“For the Baltic Sea, classified as a Particularly Sensitive Sea Area by the International Maritime Organisation, the continued use of biocidal antifouling paint on pleasure craft is particularly concerning as the Baltic Sea supports unique ecosystems already under stress from climate change and biodiversity loss.

Hempel introduced a range of biocide-free fouling release coating products (based on silicone coating technology) in 2012. Since then, says Arias, over 10,000 successful applications of biocide-free Hempel products have been made to the hulls of recreational boats across Europe (including heavy fouling water like the Mediterranean).

One of these, Silic One, provides a basically non-stick surface that fouling organisms can’t adhere to – with any strength. “Any fouling that does weakly attach is removed as the boat gets underway. In the case of slower boats, any loosely adhered fouling can be easily removed by gentle wiping with a soft sponge,” says Arias.

The non-stick science of biocide free

Arias describes Silic One’s surface as consisting of a low surface energy and elastomeric silicone matrix combined with a super hydrophilic hydrogel microlayer which sets up on immersion. This means organisms can’t attach firmly to the hull.

To achieve the required non-stick surface properties that prevent adhesion of fouling organisms, a small quantity of polydimethylsiloxane (PDMS)-based silicone fluid is present in the Silic One paint film.

“PDMS-based silicone fluids are universally recognised as safe and are widely used throughout the world in household products, medicines, medical devices, cosmetics and food,” says Arias. “In laboratory tests, PDMS showed no adverse effects on aquatic species and sediment-dwelling organisms at concentrations up to and exceeding its solubility in water. There is no evidence that it may bioaccumulate or bioconcentrate in the marine environment.”

According to Hempel, independent tests show that Silic One has consistently performed equivalent or better than copper-based biocidal antifouling products. “For example, a study carried out by Chalmers University (Gothenburg) in the Baltic Sea, Kattegat and Skagerrak areas, concluded that Silic One is more effective against fouling than the commercially available copper-based antifouling paints when immersed for two years,” says Arias. “In addition, a UK boating magazine in 2022 also highlighted Silic One performance as ‘best in test’ when tested in UK waters alongside commercially available biocidal antifouling paints for leisure boats. Other external recognitions of Silic One’s performance have been awarded in Denmark, Sweden and Finland.”

Headquartered in Denmark, Hempel has provided coating solutions to customers across the world for over 100 years. In September 2023 it announced that Silic One is available in the United States and Canada, distributed by SeaWide Distribution.

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