Suface aluminum corrosion on firewall

TylerSC

TylerSC

Pre-takeoff checklist
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TylerSC
I just re-bought my old Cherokee 140 - since I had it last it appears to have developed some "dusty" white surface corrosion on the firewall inside the engine bay. It's weird because there a very defined line between the clean metal and the corrosion area, which is at the bottom and towards the outboard direction on both sides. What is the best way to treat this? Sand it and apply corrosion-x?
 
Bell206 said:
Not enough info. A picture or two would help.
Click to expand...

Agree, some pictures would help.

I doubt the firewall is aluminum. Just a guess from the description, but the firewall may be galvanized steel and the corrosion is zinc hydroxide powder. Rainwater or condensation is accumulating in the lower outboard corners (is there a lip at the bottom of the firewall?) promoting the oxidation of the zinc coating.

If this guess is correct, sanding is not encouraged as it will remove more of the protective zinc. Preferred is to wire brush the unstable white powder completely and then use a zinc-rich epoxy paint to touch up the affected areas if a lot of the zinc protective coating has been lost.

Bottom line, first need to confirm what the corrosion mechanism is before trying to treat it, as just getting in there and sanding it may do more harm than good.
 
Last edited:
As far as I know, all the cherokees have a galvanized steel firewall. Before someone can decide how to properly preserve the surface they need to know what material they’re working with.
 
I see now that it is steel - I had assumed it was aluminum. I'll get some photos asap.
 
many Cessna firewalls are aluminized steel.

ones the aluminum is gone, it is gone.

other than a new one, there isn't many options .
 
Whatever it is, it had some minor corrosion on either side, most so around the electric fuel pump box. Looks like the previous owner got soap on it because there is an oily grime type coating on the upper parts of the firewall where there is none of the corrosion. I shot some corrosion-X right on there and will monitor. It was clearly just a little white dusty corrosion.
 
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