Time to Reconsider the Color Red for Underwater Hulls
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Jonathan R. Matias, Chief Science Officer of Poseidon Sciences Group, presented a paper at the 12th Annual World Congress of Ocean-2024 (WCO-2024) held at Aloft Novena Singapore. The paper explores the historical basis for the red color used on underwater hulls and how modern understanding of barnacle behavior challenges this tradition.
Historically, ancient Chinese shipbuilders used copper plates, while the Greeks used lead plates to protect hulls from barnacles and other fouling organisms. In 1761, the British Royal Navy pioneered the use of copper plating to prevent shipworms (Teredo navalis) and barnacles from damaging ships. By the 1840s, coatings containing high concentrations of cuprous oxide were developed, becoming a mainstay of the marine coatings industry by the 1860s.
Thus, the tradition of red-colored hulls was born and continues today, 164 years later. The fleet of bulk carriers and tankers in the Port of Singapore is a testament to how strong this tradition remains.
However, it may be time to reconsider this tradition. Research shows barnacles are attracted to the color red.
The barnacle Balanus amphitrite is one of the most ubiquitous fouling organisms in marine habitats worldwide and contributes to billions of dollars in extra fuel costs due to drag on ships. Poseidon Sciences Group has observed that once the cuprous oxide in coatings is depleted, barnacles colonize underwater surfaces in massive numbers within weeks. Over three decades of research evaluating coatings for global marine coatings companies suggest that color choice for hulls should be based on more than tradition.
A 2014 landmark study by Matsumura and Qian demonstrated that cyprids (larvae of barnacles) are attracted to red. Interestingly, adult barnacles emit red fluorescence, further attracting new settlements near older colonies. This contributes to the piling up of barnacles, forming colonies that disrupt the polished surface of coatings.
Even before the 2014 study, researchers noted that barnacle larvae preferred darker colors with longer wavelengths, such as black, green, and cyan, over lighter colors like white, light blue, and Caribbean blue.
Poseidon Sciences continues to research alternative colors for underwater hulls, aiming to extend coating performance while reducing costs for shipowners and the carbon footprint of the shipping industry. Preliminary results suggest white could be a promising replacement for red.
The data are compelling enough to reconsider whether red remains the best choice for underwater hulls. A shift to lighter colors like white could represent significant long-term benefits for marine coatings performance and environmental sustainability.
Learn more at www.poseidonsciences.com.
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