Marine

New omniphobic coating could slash fuel costs for US Navy ships

New omniphobic coating could s...
The new omniphobic coating can greatly reduce friction on ship's hulls
The new omniphobic coating can greatly reduce friction on ship's hulls
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The new omniphobic coating can greatly reduce friction on ship's hulls
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The new omniphobic coating can greatly reduce friction on ship's hulls

To make ships and submarines slippier, the US Navy's Office of Naval Research (ONR) is sponsoring the development of an "omniphobic" coating that not only repels water, but many other substances, like oil, alcohol, and even peanut butter. Anish Tuteja, an associate professor of materials science and engineering at the University of Michigan, has created a clear, durable chemical coating for ONR that is designed to reduce hull friction, making ships more energy efficient and stealthier.

Watching a ship pass, especially under sail, on a reasonably calm day seems almost like magic. As the hull slices through the water, it looks to effortlessly skim along without the slightest resistance. But that's far from true. Because the water is able to wet the hull, it clings to the surface, producing friction and therefore drag. And if the hull is fouled with barnacles and coral, the problem becomes even worse.

"A significant percentage of a ship's fuel consumption [up to 80 percent at lower speeds and 40 – 50 percent at higher speeds] goes toward maintaining its speed and overcoming friction drag," says Ki-Han Kim, a program officer in ONR's Sea Warfare and Weapons Department. "If we could find a way to drastically reduce friction drag, vessels would consume less fuel or battery power, and enjoy a greater range of operations."

Not only is reducing friction a matter of increasing efficiency, but of stealthiness as well. Friction and drag produce turbulence, which creates noise that can be picked up on sonar. Ideally, a smooth, frictionless hull would be a quiet hull that would allow ships and submarines to operate at higher speeds with less chance of being detected.

One way of achieving this is to use special coatings that repel water and other liquids rather than be wetted by them. Such coatings are well known and have been used in everything from condiment bottles to outdoor wall coatings to discourage public peeing. The tricky bit is to develop a coating with a wide spectrum of phobic behavior, so it will not only repel water, but other liquids like oil or fats. In addition, the coating must be practical, which means it must be durable.

"Researchers may take a very durable polymer matrix and a very repellent filler and mix them," says Tuteja. "But this doesn't necessarily yield a durable, repellent coating. Different polymers and fillers have different miscibilities [the ability of two substances to mix together]. Simply combining the most durable individual constituents doesn't yield the most durable composite coating."

Exactly what the new omniphobic coating developed by Tuteja is has not been revealed, but it was developed by her team using a computer database of known chemicals and subjecting them to complex modeling to predict how they would interact with one another and what their properties might be. The final product was an optically clear, rubber-like substance that can be sprayed on and binds tightly with many surfaces, yet is resistant to scratches, dents, and other abuse.

According to Tuteja, the coating has applications beyond painting hulls, including as a protectant for sensors, radar units, and antenna from bad weather. The compound is still being tested, but the team is confident that it will be ready for small-scale military and civilian use in the next two years.

The video below shows the omniphobic coatings being tested.

Source: ONR

Omniphobic Coating Tests

5 comments
ChairmanLMAO
Who gonna pee on navy ship anyway? Oh, NM!
BartyLobethal
What happens to it after it's washed off the hulls? Does it enter the food chain?
Saigvre
Of course it's in the food chain from the get-go when it has to stick to the hull instead of its inspectors! (Unfair to invasive species, barnacles protest area unsuitable, etc.) But these things manage to skip on the polyfluorinated stuff that causes trouble (plenty to see in ACS, RSC and onlinelibrary.wiley.com (Wiley-Blackwell, e.g. Angewandte Chemie)) in general. Then again this involves big wear surfaces that get annual service, so it matters how well the multi-scale surface design pattern (small-bubble-friendly, perhaps) and the omniphobicity work together to cut wake sharpness, skip bubbler noise as necessary and to distribute thrust. It is important that small craft tooling estuaries get coatings like this in a manner that helps craft integrity too. It sounds like a trivial upgrade and a challenge to not adding wind rigging to have coatings like this in use, and even to find profit in slipping around instead of navigating, maybe changing RORO cases, but accounting for each applied square cm seems like a good idea too.
CraigAllenCorson
Two things: One, if it is omniphobic, how the heck do they get it to stick to a surface like a hull? And two - will we EVER learn not to blab our secrets to the world? I know, they didn't reveal the formula, but knowing that a thing is possible is at least half the battle in accomplishing something. Now, before you know it, EVERYBODY is going to have this stuff. There goes our tactical edge.
Saigvre
Indeed, how does wax ever stick to stuff that isn't super-sticky?! ORNL may have a co-blabbing habit with private extents and a mil-to-private market chain. Tell no one. On the social no one web. https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201870123 (Though when I click on 'related' in the right tab, I do see fluorinated wax in the offering, which doesn't sound like it breaks down as well as scales.)