Pre-built tank corrosion

prkaye · #1 06-03-2007, 08:33 PM

I have identified what I think is corrosion on the outside of my pre-built tanks. It's cloudy areas that won't come clean. Two questions:

1) can or should I do anything to present this from worsening between now and the time l paint (X years) ?

2) I'm worried the some thing might exist inside my tanks. Is there anything I can or should do about that? My only access to the interior of the tanks is through the filler.

Thanks!

Phil

aparchment · #2 06-03-2007, 08:44 PM

I have the same thing on the outside of my QB fuse and was wondering what to do, so I am looking forward to the responses.

osxuser · #3 06-04-2007, 02:59 PM

You can used some aluminum polish on it to remove the cloudy area, OR if you plan on painting, even some fine scotchbrite. If you are worried about the inside, you can find someone who has a borescope and take a peek inside. I would prime after if you use scotchbrite.

Rick6a · #4 06-04-2007, 03:27 PM

Last week, I did a quick repair on an IA friend's 1974 Piper Cherokee fuel tank. Its filler flange was badly rusted and I drilled it out and replaced it with a SS one. Look at the condition of the aluminum around the new access hole I had to cut in to get to the filler flange. I stuck my camera inside the tank for a look see. You tell me if he has anything to worry about!

prkaye · #5 06-04-2007, 09:19 PM

Is it possible to alodine the inside of a sealed tank, by pouring the stuff in through the filler and sloshing it around? Or is that a ridiculous thought?

terrykohler · #6 06-05-2007, 06:34 AM

Phil:
Polishing off the discolored area (most likely just a monatomic layer of oxidation) only helps to remove the pure aluminum layer (alclad) and expose the surface to further corrosion. It's a little like picking off a scabbed over wound - it isn't a cure. If you're going to finish the A/C in the next few years, don't worry about it. If you want to feel a little more proactive, just wipe the panels down with an oiled cloth. At this point, I don't think you need alodine, or zinc chromate, or corrosionX, or epoxy,or... any other magic potion.
Keep on building,
Terry

prkaye · #7 06-05-2007, 06:57 AM

Right, but I'm mainly worried about long-term corrosion *inside* the tank. Does fuel in the tank prevent corrosion, if the tanks are kept full between flights?

terrykohler · #8 06-05-2007, 09:39 AM

Phil:
Re. the tanks. Don't alodine. Don't paint. Don't put anything inside other than proseal and fuel. Can't have oxidation without oxygen. Also, full tanks help prevent condensation as the vessel can't act as a solar still. Finally, don't worry.
Terry

osxuser · #9 06-05-2007, 11:13 AM

Quote:

Originally Posted by terrykohler

Phil:
Polishing off the discolored area (most likely just a monatomic layer of oxidation) only helps to remove the pure aluminum layer (alclad) and expose the surface to further corrosion. It's a little like picking off a scabbed over wound - it isn't a cure. If you're going to finish the A/C in the next few years, don't worry about it. If you want to feel a little more proactive, just wipe the panels down with an oiled cloth. At this point, I don't think you need alodine, or zinc chromate, or corrosionX, or epoxy,or... any other magic potion.
Keep on building,
Terry

To a good degree, the polish itself helps prevent corrosion. Sealing the poreous parts of the metal against oxygen.