Go for it lol. Id try it on a shot battery from a classic mbp or a pb. Almost anything metal can polish, i bet theres an expert in the automotive field that could do it, its just a matter of doing it the right way. And 400 grit would sand a hole lol. Your trying to polish aluminum, not sand off 8 layers of car paint
No son. I'm in the automotive refinishing industry. I was raised in it. I know a thing or two about sandpaper/polishing.
Wet-Sanding with 400 grit sandpaper is not that rough. It cuts fast, but that's what you want to take the coating off at first.
What
will sand a hole in aluminum (even thin aluminum) is 36-grit, 80-grit, or 150-grit sandpaper, On an orbital sander, and then you really have to lean into it to do that.
Years ago when I bought a pair of roller-hockey in-line skates, they had an aluminum frame. I removed the wheels, sanded them with an orbital sander and 220 grit sandpaper, then proceeded to wet-sand them with 320-grit sandpaper, and then used wet 800-grit sandpaper, then used rough compound, and then progressively finer compound until it was like chrome.
Lots of work but I got the desired effect.
I was just wondering if there were any chrome MB's floating around out there.
edit: and yes, bare aluminum needs a coating. There are sealers that companies make for wheels and such, but they are usually liquid or cream, which would not be good...YOu would really have to dis-assemble the thing for that.
As far as the LCD lid is concerned, you could just polish the top where the apple is. i wouldn't worry about the frame around the LCD. You could mask it off with plastic or masking paper. Same for the keyboard.