This may be old news but I found an alternative to sandpaper to polish out scratches and corrosion on aluminum. Regular wet and dry paper breaks down quickly and just doesn't last very long. I have some mesh or screen paper that is sold to sand drywall with. This stuff is great! It lasts a long time and cuts well. The fine grade is 220 grit so it is a little on the coarse side for fine finishing. Once it breaks down a little it leaves a finish that is fine enough to polish with scotch brite pads. The product I have is Norton Wallsand. I haven't looked but there might be finer grit mesh sandpapers available if you want a finer finish.