Corrosion under the paint

[RobertGary1]

I think I have a small area of corrosion under the paint. Or could there be any other reason the paint is chipping like this?

-Robert

[StevenL757]

Where is this spot physically located on the aircraft?

[RobertGary1]

This is upper tail fearing. Exposed to sun. Paint otherwise fine. 

 

-Robert

[Yetti]

repaint or original?  If repaint, looks like bad preparation.

[Andy95W]

looks like normal, old paint to me.  Not really corrosion, just old bad paint.  Any decent paint shop would not have a problem fixing that.

If you want to fix it yourself, use Scotchbrite and lacquer thinner and go to town until it's smooth.  Use a decent epoxy primer and good polyurethane for a top coat, or just regular Rustoleum if you just want to protect the metal and make it look better from 5-10 feet away.

[RobertGary1]

If it's not original than its nearly 20 years old. 

 

-Robert

[Yetti]

I just fixed a couple spots feather the old paint.  Rustolum White primer  build it up maybe a coat or two of primer.  Maybe some 1200 wet dry wet sanding. Then Rustolum Gloss white.  Pretty good up to about 2 feet away.

[Raptor05121]

thats just peeling paint due to either bad prep work or crappy paint. I don't see any corrosion.

[RobertGary1]

Thanks. I have aircraft etching solution, primer and glossy white paint. I wasn't sure how far i should take it down. If the surrounding paint survives a light sanding than should I still strip it?

btw this reformulated aircraft primer is the pits. Goes on like water. Zinc phosphate. EPA says the old sink chromate was giving us all cancer. 

 

Robert

 

 

[carl]

do you want some old zine cromate ?

 

[RobertGary1]

do you want some old zine cromate ?

 

yes please. Can you still get the stuff in some areas?

[RobertGary1]

Hmmm. Amazon has some $18. 

Moeller Zinc Chromate Primer, Green 025472 https://www.amazon.com/dp/B0046632GS/ref=cm_sw_r_awd_u0I7vbY6JE950

[Shadrach]

Thanks. I have aircraft etching solution, primer and glossy white paint. I wasn't sure how far i should take it down. If the surrounding paint survives a light sanding than should I still strip it?

btw this reformulated aircraft primer is the pits. Goes on like water. Zinc phosphate. EPA says the old sink chromate was giving us all cancer. 

 

Robert

 

 

Don't remove paint with sandpaper...smooth paint imperfections with sandpaper, preferably wet sanding with very fine grit. The panel has a coating of alclad and sanding the metal will breach it. Mask it and scrub it gently with a scotch brite pad. After that you have 2 choices:

1) Prime over what's left of the old paint. Try to fill imperfections with several coats of primer, wet sanding in between (1000 to 2000 grit). Plan on 2 top coats with wet sanding in between to smooth out imperfections. 

2) Chemical strip down to bare metal, etch, alodine, prime and paint.

I'd choose #1 on a 20 year old paint job...

Edited September 8, 2015 by Shadrach

[jetdriven]

Napa self etching primer 7220 will get you by until the next paint job.  Just wear a good mask because hexavalent chromium is some really bad stuff. 

[carl]

Sorry Robert ,

 

The government must have taken my good zinc chromate stuff. I can't find it  ( RV - 8 construction)   

I have some Alodine .

I've switch to epoxy primer

 

Don't remove paint with sandpaper...smooth paint imperfections with sandpaper, preferably wet sanding with very fine grit. The panel has a coating of alclad and sanding the metal will breach it. Mask it and scrub it gently with a scotch brite pad. After that you have 2 choices:

1) Prime over what's left of the old paint. Try to fill imperfections with several coats of primer, wet sanding in between (1000 to 2000 grit). Plan on 2 top coats with wet sanding in between to smooth out imperfections. 

2) Chemical strip down to bare metal, etch, alodine, prime and paint.

I'd choose #1 on a 20 year old paint job...

 

 Chemical strip down to bare metal.... My question is .  With strippers, what effect does it have on the inside of the surface? My plane has a great deal of primer factory placed inside.

I don't want to damage this primer so I don't want to chemical strip, since I will never be able to re-prime  in these hidden areas.

carl

 

[Shadrach]

Chemical strip down to bare metal.... My question is .  With strippers, what effect does it have on the inside of the surface? My plane has a great deal of primer factory placed inside.

I don't want to damage this primer so I don't want to chemical strip, since I will never be able to re-prime  in these hidden areas.

carl

 

This is why careful masking and judicious application is important. After the stripper is removed, the whole area needs to be flushed with water...lots of water. This can only be done with careful and complete masking.

Zinc Chromate seems to still be available:

http://www.skygeek.com/942.html?utm_source=googlebase&utm_medium=shoppingengine&utm_content=942&utm_campaign=froogle&gclid=CO-ZkYfc58cCFUUUHwodyqMJ0g

http://www.wholesalemarine.com/moeller-marine-zinc-chromate-spray-primer-79132.html?gclid=CJP_wMXc58cCFYyRHwodBvgPLA

 

Edited September 8, 2015 by Shadrach