Corrosion Under Fabric Aileron Leading Edges

[Steve W]

For the last two years, corrosion has been growing under the aileron leading edge fabric between the two hinges. The original aluminum was not primed before the fabric was put on. I used Stewarts System for the process. There isn’t anything happening on the two end pockets on either one of the ailerons. I am suspecting electrolysis is the cause. The corrosion is only in the area of the aluminum balance tubes. I made lead sticks the diameter of the inside of the balance tube. When the final balance was done, the tube was filled with an epoxy resin to keep everything in place. I think I constructed a pair for batteries.
Before I pull the ailerons this winter for an inside look and a recover, does anyone have any suggestions, other than a good epoxy primer, to prevent any further damage to the aileron skins? Any way of de activating the current that is causing this? The plane is hangared and the covering has been on for 7 years. I am sure the stainless steel rivets holding the tubes to the nose ribs are in contact with the lead. Appreciate any suggestions.
Thanks
Steve P203

[Nev]

Thanks for the heads up Steve. Will watch this thread with interest.

[noema]

If you cannot change the metals:
- keep any electrolyte (eg. mineralized water) out
- isolate your anode or cathode (eg paint)

... but you know that.

[Battson]

Ooo - that looks annoying. Sorry to see that!

I am far from an expert, fair warning - but based on what I've seen the seaplane guys doing to protect their aircraft, here's some suggestions.

To remove the corrosion that's already taken hold, you really want to give the underlying metal a good blast with something abrasive like sand or garnet etc. Just using plain old sandpaper isn't designed to get down into the little mircovoids created by the corrosion, and sanding it right back may result in an unnecessary loss of thickness and strength. But you may have to make do with the tools you can access, not many shops have all the right gear to address corrosion.

Then in an ideal world, you'll want to etch and alodine the metal. Make sure to get all that etching product off first though, given the nooks and crannies inside the flap. You don't want it eating away at anything over a long period of time.

Then finish with a quality two-part epoxy primer.

I can tell you from experience (non-aviation) that painting over the corrosion will not stop it completely. You need to remove ALL the corrosion first, to ensure no reagents are left under the paint to continue the reaction.