How to fix small corrosion bubble under paint?

[chuck]

I have a small area of corrosion forming on the flap, just under the stainless tape. It is maybe an inch long. What is the recommended process for cleaning it up and stopping the spread? (Will post pictures tomorrow if that will help).

[gvgoff99]

Chuck, I am answering this because I see that you do not have an answer to date on this matter. Rarely is there such a thing a a small amount of corrosion but in the event you get lucky and there is just one spot here is what I have been told. Sand it out. You actually have to get down to the bottom of the corrosion or you will have it reoccur in the future.

I am hopeful that someone that knows more than I will expand on my answer. It seems like there is a primer that will neutralize the corrosion after you have it pretty clean. But the very first step is to sand away all of the paint in the area. If the bubble is a pin head the sanding (to the metal) area is probably as big as a silver dollar and the corrosion is at least quarter size from my (limited) experience. It is sort of like cancer and you are the surgeon. You clean up an area bigger than the visable problem.
I hope this helps. George
PS Listen to Dick, I posted in the hope that you would get a more knowledgable reply. Thanks Dick!

[DickDe]

I have restored a number of aircraft & had to deal with corrosion. I would remove the flap, remove the stainless tape and check for more corrosion not only on the flap but also the rear spar. Strip the paint over the corrosion, scrub it with scotchbright & Alumiprep acid etch until the corrosion pits are clean. Flush it with plenty of water to neutralize the etch, dry it thoroughly, alodine it, then prime and repaint. This is a lot of trouble for one small spot but it is the best fix and I have done the entire interior of a Cessna like this over 18 years ago and it remains free of corrosion today.

Dick DeCramer
RV6 N500DD
130 hrs
Northfield, MN