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exhaust soot corrosion

Little Wing

Little Wing

Active Member
Noticed after a week of cold weather then a strong warm front with 100 % humidity I now have corrosion on my entire belly. Presently unpainted, how do I prevent from happening again, prime the entire belly while I wait for paint? I have an antisplat aero separator so there is no oil on the belly.

Regards,
Rod
 

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This is odd. My belly has been polished/unpainted 9 years now and had its fair share of cold weather events when I lived in the north east and never had corrosion like this. Got some smaller spots occasionally which polish out easily.

Oliver
 
If you'll be painting in the near future, I'd leave it.

If it'll be awhile until you will paint, you can prep the surface and put an epoxy primer on it. This can then be scuffed when you are ready for paint. A non-epoxy primer will not hold up in flight without a topcoat. As you probably know, most of the work in painting is in the prop, so this is not a quick job.

I don't know how long uncoated expoxy primer will hold up with no topcoat in that location. It may require sanding it off and reapplying it in any case if you wait too long.

Do you live near salt water? I'm surprised alclad has that much corrosion in a short period.
 
I'm in north Georgia. I keep a pretty good eye on the belly it wasn't there a week ago. The only thing I can think is that with the rapid humid warm up and a cold soaked plane, condensation formed on the skin and reacted with the residue? I'm gonna try removing the residue with acetone as paint thinner did not work. And then try to keep the belly clean, at least in the winter.
 
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Same problem

I had similar issues before my airframe was painted. (Plane stays the majority of the time in southern Florida near the coast). This seemed to work well on all surfaces including top surfaces. Aluminum corrosion is a finicky mistress. BTW nice looking rivets !!

Chemical Guys GAP_VKIT_16 V Line... https://www.amazon.com/dp/B00P67GSRG?ref=ppx_pop_mob_ap_share
 
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Looks like water spots, perhaps exasperated by exhaust. Try a mild solution of vinegar and water, or lemon juice and water. Try on a small area first. It might slightly etch the surface.
I would then apply a thin wax that can be removed later.

I wouldn’t get too hung up on it. If you’re going to paint, you will be shocked what your beautiful aluminum looks like after a good prep!
 
I had an area appear very similar to yours on my horizontal stabilizer. I will paint one day but got tired of looking at it so I just cleaned it up with Bonderite C-IC 33 Aero (Formerly Alumiprep 33).
 
Hi Rod. What sort of fuel are you running? One of the byproducts of combusting AVGAS is lead bromide, which is a salt. As you can imagine, salt combined with moisture, either from the air condensing on a surface or as another byproduct of burning hydrocarbons gives you a pretty good environment for corrosion. The easiest way to solve the problem is to burn unleaded fuel. Perhaps this is worth trying, if you are not already? It’s not so say that there won’t be any corrosion impact from burning unleaded gasoline, it’s just that the possibility of corrosion will be greatly reduced, both on the airframe and within the crankcase of the engine. There are heaps of posts on the forum regarding what you need to know when running mogas, including items such as vapor pressure.

Cheers.
Tom.
RV-7
 
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