Has anyone here used an epoxy/whatever product to repair pitted aluminum diesel tanks

[col50]

Here you go. Forget the epoxy.
https://www.aircraftspruce.com/menus...ksealants.html

[Oeanda]

Wow you guys are amazing. Great answers and very interesting info. Thank you.

A lot of choices here. It sounds like we don’t need to lose sleep over the idea of ripping the tanks out quite yet. Worst case it looks like we will have quite a few tricks to try first.

Originally Posted by Jim Cate

The fear of bond failure due to the normal Al oxide layer seems odd to me, for that layer is quite firmly attached to the base metal.


…Used the highly technical method of cutting out a two inch square of beer can material, folding a 90 degree bend into it and sticking it on over the leak with thickened epoxy. Was leak free for over a decade before we sold the boat, dunno after that.

Jim

This obviously sounds perfect as far as a rustic DIY fix situation goes. I wonder why I have so much trouble getting paint to stick to aluminum then?
Too much prep maybe .
Rhetorical question really- can research that…

Originally Posted by s/v Jedi

JB Weld (not the 5-minute cure etc.)

Originally Posted by nofacey

Just deal with the bad pit …JB weld

My thinking from the start was that if I wanted to do an emergency chewing gum style repair, like if I was in a real hurry, a little JB weld in the one deep pinhole (the one we have now christened ‘Bad Pit’) would probably get us by for years.
For now though, we do have time to look at it a little more thoroughly and may as well try to cover all those little rust spots, and investigate beyond the baffles.

Not sure how we got so much pitting all over the insides anyway. The tanks were installed by the PO in ‘96. I can understand pitting happening in the very bottom where water and debris sit, or in the upper part which has more exposure, but you’d think there’d be a constant protective coating of diesel in most of the lower tank. Apparently diesel isn’t all that protective.

Anyway - no point being surprised when stuff wears out and breaks. Nearly everything else has, so wtf… ha ha.

[s/v Jedi]

Sealing a tank is different from repairing a deep pit. If it would be my tank, I would first fill the deep pits with JB-Weld, then seal the whole tank with one of the polysulfide sealers.

The one people posting above mean is simply from PPG.

P/S 890 Class B is a two-part, manganese dioxide cured polysulfide compound. 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.

Here you find the webpage with links to the SDS and TDS documents: https://www.ppgaerospace.com/Product...k-Sealant.aspx

[BBill]

Regular epoxy resin is way more tenacious than JB Weld or Marine Tex. I don't have experience with aluminum tanks but have repaired broken cast aluminum outboard parts with all of them. The product that holds in the long run is epoxy resin. I use T-88 structural epoxy glue on aluminum.

If you want an eye opener to cut BS take a few different brands of epoxy and make solid cubes in an ice maker tray or just glue sample parts together. Then do destructive testing with a hammer and vice to see which is stronger. I've done this with several of the popular epoxy resins and ended up with the T-88.

Also, I used the 2 part polysulfide noted above on boats but not on metal. It's all around better than the standard Boatlife polysulfide. The Boatlife is less tenacious and not as strong or "rubbery". I purchased the 2 part from a commercial window glazing company that specialized in high rise buildings. Good stuff if you can find it in small quantities.

[s/v Jedi]

Originally Posted by BBill

Regular epoxy resin is way more tenacious than JB Weld or Marine Tex. I don't have experience with aluminum tanks but have repaired broken cast aluminum outboard parts with all of them. The product that holds in the long run is epoxy resin. I use T-88 structural epoxy glue on aluminum.

If you want an eye opener to cut BS take a few different brands of epoxy and make solid cubes in an ice maker tray or just glue sample parts together. Then do destructive testing with a hammer and vice to see which is stronger. I've done this with several of the popular epoxy resins and ended up with the T-88.

Also, I used the 2 part polysulfide noted above on boats but not on metal. It's all around better than the standard Boatlife polysulfide. The Boatlife is less tenacious and not as strong or "rubbery". I purchased the 2 part from a commercial window glazing company that specialized in high rise buildings. Good stuff if you can find it in small quantities.

Both JB Weld and Marine Tex -are- epoxy’s as well.

JB Weld has a tensile strength of just over 5,000 psi. T-88 has a tensile strength of 7,000 psi. This means that T-88 is stronger, but JB Weld is steel reinforced which is why I prefer it as a filler for a deep pit in aluminum. It works very good and is a permanent repair for this application.

That said, I have equal results with those kneadable epoxy sticks on aluminum. I have some filled holes in my masts and those repairs have held for 20 years now.

An epoxy stick is easier to use on a vertical surface, as JB Weld will run and requires a piece of tape over it while it cures, leaving a less pretty surface than epoxy stick finished with a wet finger.

[Bowdrie]

Originally Posted by BBill

Also, I used the 2 part polysulfide noted above on boats but not on metal. It's all around better than the standard Boatlife polysulfide. The Boatlife is less tenacious and not as strong or "rubbery". I purchased the 2 part from a commercial window glazing company that specialized in high rise buildings. Good stuff if you can find it in small quantities.

The two-part polysulfides go back a long time, back to the original "Thiokol" stuff which they still make today, but not in small quantities.
An off shoot was the original "Detco Grove" Teak deck sealant.
Today the "Life Calk" company still does make a two-part in sizes for the average boat owner.
https://www.westmarine.com/boatlife-...7_003_004.html

[Oeanda]

Originally Posted by Bowdrie

The two-part polysulfides

"Life Calk".

Life Calk is marketed towards sealing decks with no mention of fuel tanks.
It does come in attractively large cheap amounts compared to the aircraft versions. Is it ‘the same stuff’ ?

[s/v Jedi]

Originally Posted by Oeanda

Life Calk is marketed towards sealing decks with no mention of fuel tanks.
It does come in attractively large cheap amounts compared to the aircraft versions. Is it ‘the same stuff’ ?

No, Life Calk is thinner, pourable. It would run down the vertical surfaces of the tank.

[Bowdrie]

Originally Posted by s/v Jedi

No, Life Calk is thinner, pourable. It would run down the vertical surfaces of the tank.

It didn't show on the West Marine site I referenced, but Life-Calk makes it in a "Type H", which you basically apply with a putty knife.
And it does adhere to metal.
From their site.
"Resists teak cleaners, oils, fumes, gasoline, and diesel fuel."
From the West Marine site,
"Will bond to fiberglass, wood, metal, glass, and itself"

[s/v Jedi]

Originally Posted by Bowdrie

It didn't show on the West Marine site I referenced, but Life-Calk makes it in a "Type H", which you basically apply with a putty knife.
And it does adhere to metal.
From their site.
"Resists teak cleaners, oils, fumes, gasoline, and diesel fuel."
From the West Marine site,
"Will bond to fiberglass, wood, metal, glass, and itself"

Then this should work as good as the aircraft products.

[Oeanda]

Thanks guys.

[BBill]

Originally Posted by s/v Jedi

Both JB Weld and Marine Tex -are- epoxy’s as well.

JB Weld has a tensile strength of just over 5,000 psi. T-88 has a tensile strength of 7,000 psi. This means that T-88 is stronger, but JB Weld is steel reinforced which is why I prefer it as a filler for a deep pit in aluminum. It works very good and is a permanent repair for this application.

That said, I have equal results with those kneadable epoxy sticks on aluminum. I have some filled holes in my masts and those repairs have held for 20 years now.

An epoxy stick is easier to use on a vertical surface, as JB Weld will run and requires a piece of tape over while it cures, leaving a less pretty surface than epoxy stick finished with a wet finger.

Filling pits and holes with JB or MT is basically for low or non structural applications. They have a place but it isn't where max structural integrity is needed for load bearing. I have and use them all but they do have limitations when pushed. Sagging is a problem with all epoxies but thats a totally different topic. Like I posted already, people need to do their own testing to see the real differences...vs relying on printed info.

[BBill]

Originally Posted by Bowdrie

The two-part polysulfides go back a long time, back to the original "Thiokol" stuff which they still make today, but not in small quantities.
An off shoot was the original "Detco Grove" Teak deck sealant.
Today the "Life Calk" company still does make a two-part in sizes for the average boat owner.
https://www.westmarine.com/boatlife-...7_003_004.html

Yep, I was using 2 part in the late 1960s (which appeared to be Thiokol but was not labeled) and my comparison was with the single part Boatlife polysulfide...whether solid or liquid. I saw no difference between their solid or liquid after curing. Caulked several 32-42 sailboat hulls and decks with single part boatlife and no problems. Never used their 2 part poly so can't comment with actual experience.

[rgleason]

I haven't read the entire thread, but is there any way to determine if the back side of the alu is ok and not corroding too?

I say this because, perhaps you will want to build a fg container inside, that has its own strength.

[Oeanda]

I’m away from the boat for the holidays but when I get back there I’ll definitely be looking at the tanks more and also rereading the thread again myself. If I could remove the baffles cleanly at the welds without too much destruction (I’m doubtful of that but will check) then I could probably tuck them to one side of the tank while working in there, then stick them back in place with JB Weld or whatever. This does sound a bit hokey but when I think about it, seems like it should be totally fine for the purpose.

I wouldn’t be able to remove or insert full size baffles through the access ports w/o a lot of boat demolition.

As for the outsides of the tanks- hard to say. I think they’re probably fine but again there’s only so much access to be able to view them.
Basically no- there’s no way to determine whether or not the outsides are good, in the spots we can’t see. It’s just not worth trying to worry about it.

1- JB Weld any real pits and I’d be fine for a few years.

2 - After 1- coat the bottoms and sides with one of the recommendations here and I’d be fine for many more years.

3 - Possibly hack out enough boat structure to gain more access and line the tanks with fibreglass or something. But at that point maybe I’d be teetering towards the dreaded option 4.

4- Pull the motor, replace both fuel tanks and water tanks, and I probably don’t need to mention all the other wonderful possibilities and exciting frills that would come with this option.

After seeing how the tank corrodes, I have no huge fear of a massive fuel leak. If a tank leak develops it should be small and we will have time to save the day.

So the first step is to remove those baffles and figure out what I’m doing with that. Hopefully no huge surprises on the other sides.

Then clean and option 1. Then option 2 after that assuming we don’t convince ourselves that we need to go sailing and put off the tank repair for later. Which I highly doubt, but feel would at least be an option if somehow necessary.