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Fuel Tank & Alodine

mulde35d

Well Known Member
Friend
I am both priming or using Alodine on the interior of the RV-10 (not trying to debate the need to do so). I know you don't prime the interior of the fuel tank, but any issues doing an alodine conversion coating on the fuel tank interior.

I asked Van's if it had any effect on the adhesion of Proseal, but got the standard answer of we aren't too familiar with alodine and therefore can't recommend it.

Once again, not debating the need to alodine, just curious if anyone has experience with proseal and alodine adhesion.

The plan would be to clean / scour all the parts with Alumiprep and a scotchbrite pad, followed by the Alodine conversion coating before assembly with proseal.
 
Alodine

I am both priming or using Alodine on the interior of the RV-10 (not trying to debate the need to do so). I know you don't prime the interior of the fuel tank, but any issues doing an alodine conversion coating on the fuel tank interior.

I asked Van's if it had any effect on the adhesion of Proseal, but got the standard answer of we aren't too familiar with alodine and therefore can't recommend it.

Once again, not debating the need to alodine, just curious if anyone has experience with proseal and alodine adhesion.

The plan would be to clean / scour all the parts with Alumiprep and a scotchbrite pad, followed by the Alodine conversion coating before assembly with proseal.

Alodine is a conversion. I would abrade fay surfaces per Vans recommendation for maximum adhesion of the proseal then Alodine. Prosea should stick really well. I would think it would enhance the bond but that's my opinion. Easy to test on scrap. I bet you won't be able to remove the proseal!:D
 
I did my tanks this way, both for adhesion promotion and for corrosion protection (mostly during the couple of years the tanks have been stored in a humid, salty, dusty environment while I build the rest of the aircraft). I Alodined all the ribs, skins and stiffeners, following the specification process. Used a bath for ribs and stiffeners, brush and wipe on for the skins. The attached image shows an example.

The Proseal adhesion to Alodined surfaces was excellent. The only place I had any adhesion problem was on one of the filler neck flanges, which I didn't Alodine and obviously didn't scuff or clean well enough.
 

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I did my tanks this way, both for adhesion promotion and for corrosion protection (mostly during the couple of years the tanks have been stored in a humid, salty, dusty environment while I build the rest of the aircraft). I Alodined all the ribs, skins and stiffeners, following the specification process. Used a bath for ribs and stiffeners, brush and wipe on for the skins. The attached image shows an example.

The Proseal adhesion to Alodined surfaces was excellent. The only place I had any adhesion problem was on one of the filler neck flanges, which I didn't Alodine and obviously didn't scuff or clean well enough.

Precisely what I was thinking. Are you flying?
 
Same here, scotchbrite all mating surfaces, etch/alodine everything. PR1422 generously applied. 20 years no leaks/seeps/drips.
 
My question would be whether there's any reaction between alodine and 100LL...

There is no alodine, it gets rinsed off. While on the metal, it creates a chemical conversion process on the surface of the metal. What it converts to, I have no idea. Just know it is not alodine.

Larry
 
My tanks have been in storage for 10 years and counting. I knew it was going to be a long build, so I Alodine'd the tank parts too. I had a friend who worked in large aircraft structures, and he said the Alodine process will enhance adhesion of the sealant. As a double protection, I keep some fuel in the tanks, really only a cup full, fuel vapours keep the oxygen and corrosion away. In the 10 years, no issues. Ocassionally I pull the tank access panel off to replace the old fuel and take a look around.
 
I've been flying my -4 for 20+ years with alodined tanks (inside and out). No issues yet. When I built the tanks, I elected to use alodine as the adhesion test data shown in the mil-spec for Pro-Seal (polysulfide sealant) was based on alodined aluminum test samples.
 
My question would be why.

Exactly. Perhaps there is data on internal tank corrosion that I'm not aware of. If so I'd be interested in reviewing it. 20+ years after my first build and the tanks have no signs of corrosion.

If not then I suggest this is a solution to a non-problem.

Carl
 
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