repairing peeling paint / corrosion

[bobkiksass]

I have a few spots on my wing where the paint is bubbling or has peeled off because of corrosion underneath. I want to repair. Can anyone give advice on a method of repairing the spots.

something like
1. sandpaper
2. alodyne
3. epoxy primer
4. epoxy paint

?

Can anyone recommend specific products worth using. Thanks

 

[Tom-D]

I have a few spots on my wing where the paint is bubbling or has peeled off because of corrosion underneath. I want to repair. Can anyone give advice on a method of repairing the spots.

something like
1. sandpaper
2. alodyne
3. epoxy primer
4. epoxy paint

?

Can anyone recommend specific products worth using. Thanks

Don't use sand paper.

carefully remove loose paint with a non metallic scraper, then use a platers brush and naval jelly for aluminum to remove the black deposits. when you see no more black stuff and have a clean surface, rinse, alodine it, rinse it again allow it to dry, and prime/paint.

Platters brush, from your local welding supplier it looks like a stain steel tooth brush with a wooden handle. use it in a small circular motion do not swipe.

 

[bluerooster]

IAW with AC43.13 Sand the corrosion with 220 grit sandpaper, untill the little black spots are gone. Then treat as normal for untreated aluminum.
That being said, I feel that 220 grit is a bit too coarse, and use either 320 or 400 initially, and finish up with 600 or finer, Then acid etch, alodine, epoxy prime and paint.

 

[bluerooster]

As to specifics.
I use PPG epoxy primer, and urethane paint.
As for the acid etch, Aluma Prep works pretty good, and you can get it either from AS or almost any auto paint store. As to the Alodine, I forget which brand I use, (poured it into a squirt bottle) But I got it from AS. It does ok but not as I'd like it too.
Just remember to remove all remnants of the acid, and alodine by washing thoroghly with soap and water. lest you be "licking that calf again".

 

[bluerooster]

Correction: I referred to AC43.13 as reccomending 220 grit, I was wrong, it's 240 grit or finer, and finish out with 400. (for alclad)

 

[N801BH]

...

I am surprised that no one has suggested you investigate the extent of the corrosion before repairing the area..

 

[bluerooster]

I suppose that we're all assuming that it's been done?

 

[Tom-D]

Sanding is the old method, a fine stainless steel brush and etching will do a much better job with out loosing half the metal thickness.

 

[Gary]

Sanding is the old method, a fine stainless steel brush and etching will do a much better job with out loosing half the metal thickness.

Would that method work on repairing/replacing weathered clear-coat? This winter took a toll on some of the parts that have a blue undercoat with clear coat on top. Just wondering if that can be easily fixed.

Gary

 

[DaleB]

It may not be specifically mentioned in the AC, but Scotch-Brite can be your friend. Not the grocery store variety, but the Aircraft Spruce or Yard Store variety.

 

[Tom-D]

Would that method work on repairing/replacing weathered clear-coat? This winter took a toll on some of the parts that have a blue undercoat with clear coat on top. Just wondering if that can be easily fixed.

Gary

Clear coat is usually on top of a base paint, I'd not use a wire brush on that.

 

[edessa]

After cleaning the corrosion and before priming make sure to look up the allowable damage for that skin. IF the corrosion is deep you may need a repair not just a clean and paint. Also make sure any fasteners have not corroded. If they have, they will need replaced. As mention by DaleB, scotchbrite is your friend. I never use sandpaper.

 

[Tom-D]

As mention by DaleB, scotchbrite is your friend. I never use sandpaper.

Scotch bright is an abrasive, sand paper in a different form.

A platers brush used in a small circular motion will remove more corrosion material plus the phosphoric acid etch will do the job quicker and remove less aluminum than any other method and leave a surface that is ready for alodine.

 

[bluerooster]

It may not be specifically mentioned in the AC, but Scotch-Brite can be your friend. Not the grocery store variety, but the Aircraft Spruce or Yard Store variety.

Actually it is, not by brand name, but by description. They call it "abrasive fabric, or pad".

 

[bluerooster]

Sanding is the old method, a fine stainless steel brush and etching will do a much better job with out loosing half the metal thickness.

You still must "fair" or "blend" the worked area. IOW the pit must be feathered out much the same as you would a chip in paint.

Just digging the corrosion out of the pit is not acceptable. the pit must also be feathered out to an area of at least 10 times the depth transversly, and 20 times the depth longitudinally. That operation requires the use of sandpaper. They also go into detail about areas around rivets, and lapping adjoining skins.
AC43.13-1B sections 5, 6, 7, and 8, go into detail about the process.

 

[bluerooster]

Would that method work on repairing/replacing weathered clear-coat? This winter took a toll on some of the parts that have a blue undercoat with clear coat on top. Just wondering if that can be easily fixed.

Gary

Weathered clear coat requires the re-paint of the affected area.
You can't just re-clear it, you must also re-color it as well. And all the prepwork that goes into a re-paint applies.

 

[Gary]

Weathered clear coat requires the re-paint of the affected area.
You can't just re-clear it, you must also re-color it as well. And all the prepwork that goes into a re-paint applies.

Appreciate the reply! Kinda figured it wasn't an easy fix.

Gary

 

[edessa]

Scotch bright is an abrasive, sand paper in a different form.

A platers brush used in a small circular motion will remove more corrosion material plus the phosphoric acid etch will do the job quicker and remove less aluminum than any other method and leave a surface that is ready for alodine.

Everyone has their way of cleaning corrosion. I prefer Scotch bright. Your method has been duly noted.