Gary, good luck in your search, but I still think it's much ado about...
I represent a significant portion of the dairy and wine industries out here in California, which utilize unpainted aluminum and stainless steel tanks and panels just about everywhere. Though all kinds of stuff has been available to the maintenance folks, sometimes free from the mfgs because they want to test it in the field, the vast majority of folks use nothing but regular maintenance of the surfaces...far less than you or I would engage in for our Cobras. I suspect much the same is true for the aircraft industry...otherwise, you wouldn't have to be asking the question.
Again, as I explained...anytime you want to fix a surface blemish, you'll have to reapply (not unlike needing to reapply a clear coat on modern paint).
Why not ask Auto Union (eh...Audi) and Mercedes Benz what they use for the bare arruminum cars in their museums. Seems to me the information base of decades for showroom vehicles will be far greater than folks who have been driving around unpainted Kirkhams for less than a decade.
Again, I wish you well in your quest. I guess my remark about letting the elements "seal" it for you a bit ought to be assplained a bit more clearly. All of my research for the past 6 years since I got my Kirkham indicates that the corrosion resistence of arruminum is due to the fact that it does oxidise a bit...which prevents further oxidation. It's not corrosion-proof (not sure anything is). I guess it works a little like getting a progressive sun tan to prevent sun burn...of course, that applies only to locales where the sun invariably shins.
Best wishes.
