Little tiny brown specks, why?

[Gerarddm]

Polishing a set of Cromodora Daytona alloy wheels. Sandblasted off the old finish ( BTW, NEVER do this! What a pain getting the surface back down...), then used 240 greaseless/sisal, then 400 greaseless sisal to get the finish where I could use an emery wheel, then hand wet sand with 600, 800, then DuPont polishing compound by hand, then Simichrome final polish by hand. Put a wheel away in its cardboard box in my cold garage and came back to it in a week or two and it has tiny brown specks that are corrosion? or something, because polish didn't work and I had to go back to 400 wet sand, then back down the sequence to Simichrome to get the specks out. What is causing this? Any prevention possible?

you should be using greasless on a sprail and with wheels i polish them then clear them it saves work on the long run