Scott Will

Well Known Member
Just celebrated my 4th year of flying! But I recently got concerned when I saw this! My hangar mate (that's his gorgeous yellow Pitts you see in the photo below) pointed out two small spots of corrosion. The corrosion lies very near the right rear static port where the upper skin meets the skin below.

Anyone recommend a good course of action to deal with it? Here are the facts:
  • Quickbuild fuselage (delivery early 2005)
  • Professionally painted using PPG basecoat/clearcoat
  • Always hangared... except for a 1-2 days each year in Florida

sew_20100914-15-23-36.jpg
 
Probably an area that had a small amount of surface corrosion that did not get prepped well enough before before primed and sealed. Take down the paint around the area, re-prep and touch up the best you can. Maybe the Professional that painted the plane will warranty the work.
 
Filiform Corrosion

Looks like it. I have seem it on my current and former 50 years plus certified birds; not too big of a deal if it is dealt with early on.

Ch. 6 of AC 43.13-1B has ways to deal with it.
 
Looks like it. I have seem it on my current and former 50 years plus certified birds; not too big of a deal if it is dealt with early on.

Ch. 6 of AC 43.13-1B has ways to deal with it.

I agree.
A common cause is moisture entrapment under the paint during the painting process. It is crucial to get everything dried out well after doing the paint prep. Particularly if an acid etch, alodine, and then rinse with water process was used.
 
Fayed surfaces

Fayed or faying surfaces are common places for corrosion to occur.
http://www.eaa1000.av.org/technicl/corrosion/faysurf.htm

Some people go to extreme lengths to prevent corrosion from occuring, such as priming fayed surfaces first, riveting wet, etc. The fayed edges also need to be sealed.

My previous plane was a certified ac circa 1980, and had several areas where corrosion had developed. They all were either of two kinds, bare aluminum where the alclad had been scratched or areas where two pieces met and were subject to collecting moisture and/or dirt. The plane had to be partially dismantled and scrubbed, prepped, primered and painted. Fortunately none of the skin areas were deep enough to need replacement but it was real work to get rid of all the corrosion.

You don't mention if primer or conversion coatings were applied prior to paint, (no primer wars please).

Your two little areas may be isolated events but I would do a detailed inspection inside and out. The corrosion will have to be removed down to clean metal and then protected again. Good that you caught it early.

Dave A.
6A build