As always your project, do as you wish. Forgot to add that before. @tankerken is correct about the tracks. I was only thinking about the hull and turret. Aussie Abrams are too new to really get much rust on them. There is a good chance that the “rust” you are seeing is dirt mixed with oils, lubricant, fuel and not really rust, imo.
Here is the rustiest Abrams known to exist.
Again this is limited to a small set of tanks used by the Marines till Frenchy shows another example that proves me wrong. 