Aluminum diesel tank

[ekotopia]

Hi all. I am rebuilding a Morgan O/I 41. 1978 - that's been sitting for about 5 years - except for the trip from the keys to Virginia. ( and on that trip we used a day tank )
So I decided to pump out the fuel tank - about 80 gal. of fuel - and the stuff that came out was really foul. So I decided to cut a manhole and check it out. U cant belive how it looked - about 1/2 to 3/4" thick sludge stuck to the only slanted surface( about 14" at 60 degree angle the whole lenght of the tank - about 6' ) and on the bottom !!?? Nothing on the vertical areas ??
The bottom (about 6" wide ) was also covered with sludge above the suction pipe - about 1 1/2". I cleaned the tank and scraped of some hard stuff - I guess corrosion stuff -and the slanted surface and the bottom is pitted - nothing else ??!! Not the baffles or the side walls.
I poked the pits and found out that they appear to be from the inside ( they bottom out in about a 3rd of the thicknes on the slanted surface and about 1/2 on the bottom. Any ideas of why this is and how to treat the tank to be able to keep it. Is there a paint or epoxy to seal the pits with??
Cheers

[cardiacpaul]

uhhh, get a new tank. period.

[sailboy21]

what he said..

But if you want to be cheap about it marine-tex sticks like something nasty to wire brushed solvent free aluminum . But.. to be fair let the next owner know what you did

[CharlieCobra]

Glad my tank is Monel.

[Rockter]

Two part polysulphide sealant will do it. It sticks like, well, glue, and does not let go.

[sailingdog]

Rockter-

I don't think polysulfide sealant is a good idea in a diesel tank. Epoxy is far more fuel resistant IMHO.

[artbyjody]

If you haven't seen this [Click Link: article before]: Probably a decent guide if you are going to do it yourself.... Although - I would consider just removing the tank and take it a machine shop in town and have them cut out the base of the tank and weld in a new one...

[ekotopia]

Thanx for responds - but does any have a clue to why the sludge and pitting was only on the slanted surface . The bottom I can understand, but why not on verticals?
As of removing the tank -
only in pieces - its 120 Gal. under the side deck next to a center cockpit.
Love to hear more....
Cheers

[Rockter]

Oh Saildog, thou ist contrary...

It's been on that tank for 10 years now and the water tank.

Apparently it was even rated for gasoline.

Epoxy is a bit brittle methinks and polysulphide has done it for me and still does.

I put it on with a roller after a mammoth degreasing session.

[artbyjody]

Originally Posted by ekotopia

Thanx for responds - but does any have a clue to why the sludge and pitting was only on the slanted surface . The bottom I can understand, but why not on verticals?
As of removing the tank -
only in pieces - its 120 Gal. under the side deck next to a center cockpit.
Love to hear more....
Cheers

Its called varnishing...the diesel and whatever containments over time of non-use start a chemical reaction - since fuel evaporates - this becomes more concentrated - and the sludge contains more by products than fuel and thus the aluminum at the bottom gets attacked more ferociously.... large enough tank you may get away with the previous link suggestion I posted...