aluminum and epoxy bonding

[geoshep]

I have twin alunimun diesel fuel tanks. There is signs of pitting and corrosion on the aft ends, bottom welds. The rest of the tanks look fine. Without removing engines (tanks are large 150 gal ea side) is there a proven epoxy that will seal over the welds to prevent and pinhole leakage.

[Stumble]

Geo,
I went through this last year and decided to just replace the fuel tank. The problem is that if one are is corroded there are likely places that you can't see that are in the same condition. That being said while there are some epoxys that might work, the better option is to patch weld the tank where the corrosion is problematic.

[geoshep]

thank you for your reply. Yes removing the tanks is on my mind...means both engines, transmissions, exhaust, etc must come out and I will probably do it..but in my demented way of thinking we can build a space ship with glue on heat tiles that withstand trips to space subjected to immense heat, pressure and we can't make a foolproof epoxy to metal. There must be a product?

[rasorinc]

3-m mmm has a marine dept. you can adhesive metal to metal and wood with their products. Research their site or e-mail them or call.

[messabout]

My manufacturing operation has been using epoxy to glue stainless steel rods to an aluminum bar for years. Failures are very rare. That is all well and good but if one of my adhesions fail it is merely an annoyance. If your gas tank fails it it is not a mere annoyance, it could concievably be fatal.

The prospect of removing the engines and the rest of the stuff is not a welcome one. Don't let that stop you from doing the job the right way, the safe way.

[yipster]

Alu needs a speciality grounding paint before epoxy
its done in airplanes, more on the net and in early'r discussions on the forum

[PAR]

Aluminum bonds well with epoxy, assuming the prep is proper. This isn't the issue in this fuel tank situation. The problem, as has been pointed out is the very strong likelihood that more then just one pin hole exists in the weld beads. Given this probability, you have to fix the tank with more metal. You can fix this single leak with epoxy, but like others here and having gone through just this issue myself, you're just going to be "chasing your tail" with this, using epoxy. You'll seal leak after leak, until you just want to climb a water tower with an AR-15 and start picking folks off.

[dinoa]

If despite the warnings you decide to slosh the tanks with a sealer try a polysulphide sealer like Proseal or a Buna-N sealer like PR-1005-L

Dino

[upchurchmr]

Lots of Aircraft and also car restorers use a fuel tank sealant. I have used them for motorcycle tanks and have never had an instance of failure even after lots of years. They stopped rusting from inside the tank - there were no pinholes just interior rust and a seam leak from damage (a dent).

I assume you would still have to remove the tanks, because you have to clean out the tank and roll the tank around to try and evenly coat the sides, especially the seams you are concerned about.

[wet feet]

For any kind of sealant to work after the tanks have held diesel you will have to be extremely thorough about preparing the tank.Can you find any evidence to suggest that there might be a sealant suitable for this application?I don't know of any aircraft or motorcycles that run on diesel,although I believe there have been some long ago.
Given the amount of work it will take to remove the tanks and the uncertainty of a successful repair,not to mention what your insurers may have to say on the subject,new tanks may be the best long term option.A repair may mean taking the whole boat apart again in a few months,or at best a year or two.

[upchurchmr]

Gentlemen,

The motorcycle example I used was certainly gasoline.

Military aircraft jet fuel is more akin to desiel than gas since they also don't want a very explosive fuel. We use fuel tank sealant every day, and use it for original build and repairs.

Sorry I can't give an exact fix.

Perhaps I didn't get as specific as I could have. We do not use epoxy for any reason for sealing, we use polyurethane sealant.

Marc

[ddrdan]

Just a novice here on marine applications, but, wouldn't it be easier to cut the top off the tank, in place, install suspended bladder tanks and use the top to make a cap to go over the old tank and the new bladder?