Polyurea - a way to prevent leaks and protect metal from rust/corrosion in salt water

(Chad Elwartowski) #1

Polyurea is a surface coating that is sprayed on and dries in seconds. It is rubbery and sticks very well to metal (concrete requires some preparation and I have seen first hand that it tends to peel off of concrete surfaces). It is very very durable and algae/barnacles has a hard time attaching to it.

It was used for the San Mateo Bridge, the Boston Tunnel, US Marines amphibious vehicles and is starting to be used in a lot of backyard ponds, underground bunkers, roofs, ships and more. Most people would be more familiar with the coating in the back of modern pickup trucks which is polyurea.

Coca Cola uses it for their water tanks

It has been shown to protect against explosions

Sprayed onto boat hulls

fully coated boat

Makes objects water tight

Modular Extension | Connectors | Cellular expansion | Building Technology
The power of Polyurea
Introduction- Productivism and Constitutional Capitalism
(Larry G) #2

Poly Urethane foam is also approved for marine use and provides up to 60lbs of buoyancy per cubic foot.


It’s a bit more expensive than some more traditional or recycled materials, but is a closed-cell material, so it won’t absorb water over time like logs do. It should have very good durability in seawater, but may still be penetrated by sessile sea life if left exposed. It’s not a structural material, but can be used to fill other structural spaces so that the integrity of the float isn’t subject to catastrophic failure and sinking if hull integrity is compromised by cracking or holes. for example, a concrete caisson.

A single drum of it will fill 500 cubic feet and provide 30,000 lbs of buoyancy after expansion.

(Chad Elwartowski) #3

Polyurea and polyurethane are different materials.


Could you give the urls for those videos, please? I considered the truck bed spray-on as a paint years ago too, and found the same problem as when i looked for spray-in foam application companies: i got laughed at. Strangely, same happened here when i said i didn’t need waves to float a boat.

(Larry G) #5

Agreed, I was just thinking that perhaps there needs to be a thread specifically about materials, and yours popped up.

(Chad Elwartowski) #6

I’ve been following the polyurea world since 2008. I never brought it up here because I had planned on starting a seasteading business and polyurea was going to be my “special sauce”. I have not seen it brought up here before.


Excellent example of splitting functionality of a system into separate departments, in a way that works on the strengths of each to cancel the weaknesses of the other.

(Chad Elwartowski) #8

Here are some links to a polyurea spray machine ($7000-$12000) as well as the material ($3-$8/kg).



I saw some on Ebay a while back too.

(Chad Elwartowski) #10

Ya, just showing that the system is not too expensive. I would fully expect someone to set up a polyurea business on a seastead to be hired to spray any exposed metal or for spraying boats.

(Wilfried Ellmer) #11

I can see this material play a role in freeforming and form on the fly of extreme light floating structures.


It’s paint, not structural.


I also have a “special sauce”, it’s been on a few pieces of steel for ~5 years now, and has both stopped rust and prevented rust from starting. And it’s fairly clear, so i can see the steel thru it. Buying it retail has not been cheap, and the (usa) oem companies won’t lower the price for large boat-sized purchases.

That’s extremely frustrating about usa companies, they’d rather not sell than sell cheaper. I discovered last nite that despite a R-410 freon factory existing a couple of states over from me, and all the patents being in usa company hands, it’s cheaper to import the stuff in (25#, 50#, etc) barrels from China.


Does anyone know how marine life reacts to polyethylene? Very little sticks to it, in terms of glue and other man-made adhesives. But it does not come in boat-shapes.


When I read Polyurea: Poly=Many…Urea=pee

Polyurea = many pee


Pee is actually a good source of ammonia and other nitrogen products, for fertilizers and fuel.

(Larry G) #17

I’ve got this one, too:

(.) #18

poly urea is a medical term for large volume of urinary output

(Bob LLewellyn) #19

[quote=“KatOnTri, post:14, topic:767”]
But it does not come in boat-shapes.[/quote]

I believe that it comes in two liquids that when mixed together foam and swell up like a can of great-stuff.
But that might be polystyrene, my chemistry is weak.


Polyethylene is what that tubing you use for the home RO is. Or as a sheet, as paint tarp (slightly clear or black). It’s not a foam.