Originally Posted by dexntex
It is a Hoppe's (or Outers?) phosphor bronze brush. The shaft is silver-colored but I believe it is not aluminum and is probably steel because it is strongly attracted to a magnet (and not just the base part).
Then I simply don't know. A mirror shiny bore and sharp rifling is where I stop cleaning and call it a day, like most owners. I would guess that there is always a layer of oxidation, which, once removed, quickly builds up again. Good luck with your research.