Coating for inside NEW aluminum holding tank

[Rowglide]

OK First off, I know, I know... aluminum is not suitable for holding tanks. But...
My boat came with a brand new 38gallon tank (Florida Marine Tanks). PO had it made as a replacement to the existing tank. It is BRAND NEW. and equally important, IT FITS! If it only lasts 5 years I am OK with that, if I can make last longer great.
What I would like to know is if there is a coating that can be applied inside the tank that would minimize the effects of waste on the aluminum. Either a wand sprayed coating or a liquid that could be poured in then sloshed around.
Jim

[Captsteve53]

I had heard of this pour in compound via a third party so can not vouch for it's longevity but suitable for Aluminium tanks and at least reads good in the advertisement,

Cant really think of any other way apart from cutting a hole and doing the normal prep for Aluminum and then Primer Epoxy coatings finished by Epoxy coal tar .then make a tank top that bolts in place,

Link to the above pour in compound :https://www.kbs-coatings.com/tank-sealer.html

Cheers Steve

[Terra Nova]

Originally Posted by Rowglide

...is if there is a coating that can be applied inside the tank that would minimize the effects of waste on the aluminum...

No. Replace it now or after it contaminates your boat.

[model 10]

There are a couple of aircraft fuel tank sloshing sealants that would work. Randolph makes one that is acid proof also.

[peghall]

FL Marine Tanks used to coat the insides of holding tanks with (IIRC) an epoxy. So I suggest you ask them what if anything you can do. However, even if you can, if even a hairline of exposed metal remains, urine will eat through it. There's also the matter of expansion and contraction due to temperature changes--and there can be some pretty ones in your neck of the woods--that can put cracks in the coating.

So my advice: Sell it and replace it with a plastic tank. It hasn't been used, so it can be converted to a water tank. There are several mfrs who offer a variety of shapes and sizes:

Ronco Plastics Ronco Plastics marine Tanks is the best source...they make TOP quality thick walled tanks and have more than 400 shapes and sizes, over 100 of which are non-rectangular (which means you might be able to fit a larger one in the same space), and they install fittings in the sizes and locations specified by the customer when they make the tank.

Others include Trionic Trionic , Duraweld DURAWELD If you can't find a mold that fits, Triple M Plastics in Maine makes top quality custom molded tanks Triple M Plastic Products Inc

Yes, replacing the tank now will be expensive...but you'll only have to spend it once instead of paying to have your aluminum tank coated inside and then spending the money in a few years to replace it.

[David M]

Three coats of a two part epoxy like Interlux 3000 would work.

[boatpoker]

Previous owner installed an aluminum (epoxy coated) waste tank. Thought I could get 2 years out of it.
I was right, 2 yrs and she's done ! Guess what my first job is when I get back to the boat next week

[a64pilot]

My boat came with an aluminum tank 30 years ago, was replaced once. I just replaced it the second time with a plastic one from triple M in Maine, I would use them again, they made the tank exactly to my drawing. You can also send them a tank and they will replicate it.
The tank I replaced was 12 years old and about to go, it had been lined, you could tell cause whenever you pumped it out, it looked as if it was full of egg shells, little white flakes that were the lining.
If it's a good thick tank made from a good alloy and lined, you should get ten years out of it, maybe.

The plastic tank also allows an external sensor gauge to be fitted, I used a profile gauge and it works perfectly. Aluminum tank requires an internal sensor, something I didn't want to have to remove to clean etc.

[thinwater]

I'm with Peggy on this. I've been around lots of coated tanks in the chemical industry, and unless very special procedures are used (impossible) and a reinforced lining is used (impossible), there will be a small crack and it will fail soon, making a mess.

[JPA Cate]

Rowglide,

Thinwater wrote that when it leaks it will make a mess. Yes, and thati's like sewage getting into places in your boat that are very hard to clean and get odor-free afterwards.
Imho, hauling around your fermenting waste products is bad enough, but waiting for the first hint of smell to deal with it would be fairly awful, too.

Peggy and Terra Nova have this one right, imho.

In fact, it may be time to consider an upgrade to a composting/dessicating toilet.

Ann

[Lodesman]

Originally Posted by Rowglide

What I would like to know is if there is a coating that can be applied inside the tank that would minimize the effects of waste on the aluminum. Either a wand sprayed coating or a liquid that could be poured in then sloshed around.
Jim

You might look at POR15 POR-15 Rust Preventive Coating - Stop Rust Permanently
Apparently it will bond to properly prepped aluminum.

[estarzinger]

Listen to Peggie.

Do it once, do it right.

Getting a perfect plastic one is on the easy and inexpensive end of marine jobs to to.

[boatpoker]

Originally Posted by a64pilot

My boat came with an aluminum tank 30 years ago, was replaced once. I just replaced it the second time with a plastic one from triple M in Maine, I would use them again, they made the tank exactly to my drawing. You can also send them a tank and they will replicate it.
The tank I replaced was 12 years old and about to go, it had been lined, you could tell cause whenever you pumped it out, it looked as if it was full of egg shells, little white flakes that were the lining.
If it's a good thick tank made from a good alloy and lined, you should get ten years out of it, maybe.

The plastic tank also allows an external sensor gauge to be fitted, I used a profile gauge and it works perfectly. Aluminum tank requires an internal sensor, something I didn't want to have to remove to clean etc.

Is your boat in salt or fresh water ?

[model 10]

The worst corrosion found in an airliner is often the structure underneath the heads.

[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.