Tinta para navios

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Tinta para navios
« em: Março 12, 2005, 02:50:15 pm »
"A new environmentally friendly coating based on sharks' skin may soon help the U.S. Navy increase ship speeds while saving fuel," Wired News reports.

The coating... will be applied on the hull of ships below the waterline, where all manner of algae, barnacles and other wee beasties attach themselves, slowing ships and reducing their maneuverability...

Of the $550 million to $600 million the Navy spends annually on powering its ships and submarines, at least $50 million stems directly from drag due to marine growth fouling the vessels' hulls, said Stephen McElvany, an environmental quality program officer in the Office of Naval Research's physical science division.

Existing antifouling paints such as tributyltin, or TBT, kill algae and barnacles when they latch on. TBT is being banned worldwide by... the U.N. body responsible for overseeing shipping-related issues...

To find a way to persuade algae to move on rather than killing them, Anthony Brennan, a University of Florida professor of materials science, and his colleagues turned to nature. Sharks don't have algae or barnacle problems despite being underwater all their lives. Shark skin is made up of tiny rectangular scales topped with even smaller spines or bristles. This makes shark skin rough to the touch. This irregular surface makes it difficult for plant spores to get a good grip and grow into algae or other plants.

"It's like trying to walk across a bed of nails when some nails are longer and unevenly distributed," Brennan said.

Using a combination plastic-and-rubber coating, Brennan replicated a version of shark skin that is made up of billions of tiny raised, diamond-shaped patterns, visible under a microscope. Each "sharklet" diamond measures 15 microns, or 15 thousandths of a millimeter, and contains seven raised ribs that resemble different lengths of raised horizontal bars.

In lab tests, the coating -- provisionally named Gator Sharkote -- reduced by 85 percent the settlement of spores from a very common and detrimental type of algae called Ulva, a green seaweed often seen on the sides of ships.

"The only place the spores land right now is where we have a defect in the pattern," Brennan said.

The Navy has had a wicked case of shark envy, lately. A few months ago, the service started looking into how sailors could use sharks' electric sensors to spot underwater mines.
Ai de ti Lusitânia, que dominarás em todas as nações...