Epoxy Lining an old aluminum diesel tank

[Tafa]

Hello everyone,

We've seen a boat recently and seriously considering her. One of the concerns I have; the old aluminum diesel tank has been lined with epoxy sealer 7 years ago.

Sellers says that the tank has been pilled out and sent to an automotive tank refurbish shop for the treatment and done professionally. I assume the lining material is something like this https://www.kbs-coatings.com/tank-sealer.html

My question is, how much life should be expected for that kind of fix?

Many thanks in advance

Tafa

[skipmac]

Hi Tafa,

I think the life of the epoxy lining would be impossible to determine without inspection of the interior of the tank. Even then, unless there is obvious and visible damage to the lining it could be difficult to tell if the lining is close to failure or leaking. The lining could be separating from the metal without showing any surface damage.

Any idea why the tank was lined? Was it leaking already? If leaking, was it from a seam or more serious corrosion that impacted a large area of the tank.

Worst case, if the tank was removed once then I would assume it could be removed again. Since it has been epoxy lined I think it would be impractical to remove the lining and weld new metal or weld bad seams to repair the tank. But you could have a new tank made to fit the spot. Cost of course will depend on the size and shape of the tank. For my boat I priced a new, 40 gallon tank at about US$700. Installation of a new tank, IF you have access, isn't that big a deal.

If you love the boat otherwise I would just factor tank replacement into your bid.

[a64pilot]

The real question is why was it lined to begin with?
My bet is a temp fix for a leak. If it can be removed to be lined, then it can be replaced.
However an aluminum fuel tank ought to last pretty much forever, or until it corrodes from the outside. Diesel fuel isn't corrosive to aluminum, water is of course as can dissimilar metals, keep them out and keep the outside of the tank dry and it ought to outlast you.

My original aluminum fuel tanks in my 1946 Cessna are in excellent shape, and they are very thin and lightweight compared to a boat fuel tank.

[skipmac]

Originally Posted by a64pilot

However an aluminum fuel tank ought to last pretty much forever, or until it corrodes from the outside. Diesel fuel isn't corrosive to aluminum, water is of course as can dissimilar metals, keep them out and keep the outside of the tank dry and it ought to outlast you.

Usually correct but the diesel tanks in my boat corroded from the inside. The PO never cleaned the tanks or pulled the water and sludge out of the bottom. There wasn't much but what was there was corrosive enough to eat holes in the aluminum from the inside and start leaks.

I posted pictures on an old thread showing the corroded area on a piece I cut out of the tank. Looked like someone had poured acid on the metal.

But yes, keep the diesel clean and DRY and the tanks should last forever.

[UNCIVILIZED]

If the tank doesn't already have an inspection port (or two) it's worth adding one. That way you can see what's going on inside of it, even if you have to use a borescope. Which are relatively cheap.


One option for the tank is to mummify it' exterior in epoxy & fiberglass. Taking into accound how much it may swell or contract with temperature changes. Which sometimes means making a few relief cuts in the metal. But then you have a fully watertight "fiberglass" tank with an aluminum lining. And from there it should be pretty much mainenance free, aside perhaps from the fittings for the fuel fill line, vent line, & fuel lines to the engine.

[hpeer]

Aircraft use a 2 part goo that seals the cracks between aluminum sheets in order to make their tanks.

I believe it works on fg as well. Boat Life, yes the caulk folks, sells it but it's cheaper to buy from aircraft dealers.

PR-1440 Class B is an aircraft integral fuel tank sealant. It has a service temperature range from -65°C (-54°C) to 250°F (121°C), with intermittent excursions up to 275°F (135°C). This material is designed for fillet sealing of fuel tanks and other aircraft fuselage sealing applications. The cures sealant maintains excellent elastomeric properties after prolonged exposure to both jet fuel and aviation gas.

PR-1440 Class B is a two-part, manganese dioxide cured polysulfide compounds. The uncured material is a low sag, thixotropic paste suitable for application by extrusion gun or spatula. It cures at room temperature to form a resilient sealant having excellent adhesion to common aircraft substrates.

[Tafa]

Thank you very much everyone,

The seller said, he noticed a small leak on one of the seams and pulled out the tank, sent for the lining process. The bilge seems clean and free of odor (the tank sits in the bilge) No sign of a diesel leak at all.

The tank seems sealed both inside and out and it looks like properly done. with no inspection port. I will get a borescope (thanks for the idea) and be sure inside is clean.

Probably I will move forward with an offer while keeping potential tank issue in mind.

Thanks again all.

Tafa

[johnrid123]

WE USED A 2 PACK EPOXY FLOOR SEALER RESISTANT TO OILS AND WATER, WORKED A TREAT ON AN ALUMINIUM FUEL TANK IN A 89 BAYLINER 2858

[Cheechako]

Originally Posted by a64pilot

However an aluminum fuel tank ought to last pretty much forever, or until it corrodes from the outside. Diesel fuel isn't corrosive to aluminum, water is of course as can dissimilar metals, keep them out and keep the outside of the tank dry and it ought to outlast you.

Both the aluminum tanks in my little trawler were corroded and leaking. The tanks were removed and new bottoms welded on them by the next owner. I would have went plastic, but it worked out.

[Kita]

Originally Posted by skipmac

Usually correct but the diesel tanks in my boat corroded from the inside. The PO never cleaned the tanks or pulled the water and sludge out of the bottom. There wasn't much but what was there was corrosive enough to eat holes in the aluminum from the inside and start leaks.

I posted pictures on an old thread showing the corroded area on a piece I cut out of the tank. Looked like someone had poured acid on the metal.

But yes, keep the diesel clean and DRY and the tanks should last forever.

Time to start thinking new tanks,if corrosion is bad enough on inside for holes then fuel problems will just come back to be trouble. ... fix the problem that will save headaches later....

[Seighlor]

Both 140 gallon aluminum tanks were leaking when, several years ago, I purchased a 1988 trawler. A phone conversation with one of the technicians at West Systems provided a cure that has worked well.

We began by installing in each tank a 14" inspection plate system purchased from SeaBuilt NW LLC. This was followed with a thorough grinding away of the oxidized aluminum and installation of a patch, following the directions provided by West Systems.

It was't what I would describe as a quick and easy fix but it was a lot easier than pulling the tanks might have been and it did save a lot of money. West Systems assured me the patch will be permanent and, to date, it's been a 100% fix.