The wheels were originally polished and then coated with a clear lacquer or enamel. That's either chipped or flaked away and the exposed aluminum has oxidized, developing what looks like what you describe as white mold. You can get small buffer wheels to be used in a power drill. They come in a variety of materials. To clean without damaging, use the type that look like the 3M Scotchbrite pads used to clean glass stovetops. Different colors are used to identify the abrasiveness. I believe the black ones are most abrasive. I use a brown one.
It takes a little work, but you can clean the wheels pretty good with the brown buffer wheel. Then use a good aluminum polish. I have some metal polish that comes in a stick. It's called polishing rouge. I use a cloth wheel for that. Spin the wheel against the end of the rouge, then apply the wheel to the lip of the wheel. It turns black as it polishes, bujt that wipes off with a cloth. Afterward, apply a good coat of automotive wax to protect the polished surface.
