Firewall

I've realized I can't put all the controls back into the cabin until I clean up the light rust on the firewall.

Also, all the Tinnerman nuts are rusted and some are broken.  Since they're riveted through the firewall it would be tough to get at them once the rudder pedals, etc. are in the way.  I've ordered new Tinnermans.  One thing I realized is Cessna used plated nut plates and all you can get today are primed.  I think I'll add some paint, probably silver, to give them a better chance against rusting.  I'd like to think I've learned form all the rusty steel parts I've been cleaning which were only primed. 

The Tinnerman nut strips (A6221-8Z-8-D) used on the edges of the firewall for attaching the cowl are no longer available.  I read a posting at the club site where the person carefully riveted new nut plates to the strips in places where the little spring tabs had died.  I'm just going to make new strips from aluminum and rivet the nut plates to them.  Using Matched hole construction, remember the Thorp T-18, I can make the new strips faster than fixing the old ones.

The other thing I expected to find at the club site was a good recommendation for painting or treating the firewall to stop the rust, no such luck.  The firewall is Ternplate, think steel coated with 90/10 lead/tin solder.  They don't make it anymore because of the lead thing and cancer.  It's what was used to make the gas tank on my WACO NINE, 83 pounds of steel, rivets, and soldered joints.  Originally I thought it was galvanized steel so I was going to clean it and lightly treat it with Corrosion-X.  Galvanized is coated with Zinc and resists rust even at minor scratches.  It has to do with the galvanic action of the Zinc.  Ternplate has no such galvanic action, scratch it and it rusts.  I suppose you could re-solder the affected areas. That sounds like to much work except where you need a ground strap attached. If I were doing a restoration I might replace the firewall, but I want to fly this thing before the grandkids turn into teenagers.  So, I'm going to lightly clean it up and paint it with some Rust-Oleum probably a high temp version.  I don't like the idea of painting a firewall in case of a fire.  They make a paint which can be used on exhaust pipes but it has to be cured at those high temps, not practical for a firewall.