I’m no “expert” on the AR Teflon question.
I do however work at a helicopter depot overhaul facility, and have vast experience with aluminum, titanium, stainless steel, and cobalt (all of which are normally alloyed).
As aluminum goes, it DOES corrode! It will not rust, rather, it will turn into a chalky white powder. Galling is usually caused by two similar metals contacting and having friction (most notably stainless steel), this doesn’t seem to be an issue here.
Aluminum should ALWAYS have some form of corrosion treatment, be it alodyne, anodizing, plating, or Teflon coating. Furthermore, corrosion will be accelerated by the contact of dissimilar metals (i.e. bolt carrier to upper receiver).
How long it will take for this corrosion to be evident will be determined by environmental conditions (temperature, humidity, PH levels, etc). Lubricant used on the weapon will most certainly slow the corrosion by providing a protective barrier. But, rest assured you WILL have a corrosion issue with the bare aluminum, just a matter of when.
Hope this sheds some light.
Oh- I could just be anal about this too. [8)]