Coating for inside NEW aluminum holding tank

[peghall]

In fairness...coated or bare metal, he can get at least a couple of trouble-free years out of the aluminum tank, and as we all know there's always more than enough that you have to spend money on the first year you own any boat, new or pre-owned.

So the only really urgent reason to replace it now is the opportunity to sell it unused as either a water tank or a waste tank. But replacement in a max of two years--before it starts to leak--should definitely be at the top of his fall 2019 to-do list.

[model 10]

I don't know how poop compares to jet fuel or some AG chemicals but a polysulphide coating on the inside of tanks works pretty well, or most of you would be dead.

[UNCIVILIZED]

What about wrapping the aluminum in a structural thickness of epoxy & fiberglass, & installing fittings into the glass. So that essentially the aluminum is but a mold (& faux liner). One might have to do a bit of modifications to things, in order to account for flexing & swelling, but an epoxy/glass tank should work I'd think. And in this case it'll fit the space well, knock on wood.

[a64pilot]

Originally Posted by Guy

I don't know how poop compares to jet fuel or some AG chemicals but a polysulphide coating on the inside of tanks works pretty well, or most of you would be dead.

Cost to cost the inside of an aluminum tank with fuel tank sealer is likely to be close to the cost of a plastic tank.
And while Peggie is way more qualified on waste tanks than I am, mine lasted a whole lot longer than two years, it didn't fail but was about to, interestingly it was failing from the outside. Leaking chainplates and condensation kept the bottom corner side wet, once enough aluminum oxide fell of, it was like wet sand apparently and kept the tank wet. Boat has always been a salt water boat, but I changed to fresh water flush a couple of years ago.
Pics of old tank and new plastic tank of course

[Rowglide]

Originally Posted by boatpoker

Is your boat in salt or fresh water ?

For at least the next 6 years, Fresh water. Maybe by then they will have designed a decent composting toilet.

[boatpoker]

Originally Posted by peghall

When it comes to waste holding tanks, it doesn't matter whether the boat is in salt or fresh or whether the toilet flushes with sea water or onboard fresh..'cuz it's urine that destroys metal holding tanks.

Having experienced both. I have found the combination of urine (urea, uric acid, sodium, chloride) and salt (sodium chloride) to be considerably more corrosive.

[Chuck Hawley]

At the risk of having everyone repeat their opposition to aluminum holding tanks, the material I would use to coat the inside would be regular old West Systems 105/205. I think the tumbling idea could work, but it would be hard to determine if every square inch was coated, and obviously any gaps would be problematic. 105/205 is highly water resistant, low viscosity, bonds well to clean surfaces, etc.

I am not sure what you would do at the inlets and outlets since you'd, once again, not want any exposed raw aluminum

Cheers,

Chuck

[KP44]

You'll will hopefully find the tank is already coated on the inside.

[Captndave1]

Aviation fuel cell sealer would be the best bet. It can be obtained from most aviation supply houses.

[boatpoker]

Originally Posted by Captndave1

Aviation fuel cell sealer would be the best bet. It can be obtained from most aviation supply houses.

Back in the days when I had a Triumph motor cycle collection I used this stuff to coat the insides of the notoriously leaky tanks

[Scout 30]

I think Uncivilized has a good idea. It's pretty easy to glass the outside of a tank. I'd use epoxy & just do the sides & bottom.

[Rowglide]

Well her is the plan...
I will be getting a fuel tank sealer from Aircraft Spruce and "sloshing" the inside very carefully, (I can see throughout the tank throught the fitting / level gauge holes)
Then I will follow up with a glass / epoxy wrap over the entire tank. The only place I cannot really cover is the threads on the fitting hole, but they are really heavy aluminum (Over 3/8" thick) so I won't lose too much sleep there, may use tank sealer as thread sealer when installing fittings.
And then we will start the clock. Tanks is a breeze to install / remove so if it has to go at some time in the 2-3 year future, it'll only take a few hours to deal with it.
I'll report back with results, but don't stay up waiting, it could be quite a while.
Jim

[boatpoker]

Originally Posted by Scout 30

I think Uncivilized has a good idea. It's pretty easy to glass the outside of a tank. I'd use epoxy & just do the sides & bottom.

Unless you use a macerator.

[boatpoker]

Originally Posted by Rowglide

I'll report back with results, but don't stay up waiting, it could be quite a while.
Jim

or not .......
Hope it buys you as much time as you'd like

[a64pilot]

I don't know of any aircraft fuel tank sealer you can "slosh"
Normally it's either "A" or "B". A being thinner and about like 5200 in viscosity, the B is thicker and won't run nearly as much, about the same as silicone sealant.
Then there is what we called Monkey Blood which is red and watery, idea was it would seal leaks that were there after normal sealant. Never had any luck with it. I would not recommend it.
Both the A and B types would take an access cover and application with a brush.

I'd either just install and live with it, or install a plastic tank.
The tank in the pictures I posted had 2002 written on it and the hoses, making me assume they were replaced in 2002, I put the plastic tank in early 2017, so 15 yrs?
However I am of the opinion that most of those 15 years the boat sat unused, if that's worth anything.