Aluminum Oxide: "White Rust" on aluminum parts is kind of a neat flavor of corrosion. It's "self sealing", meaning that once it covers the surface, it will keep moisture out and prevent the part from corroding further. Cleaning it can be done with a medium grit sandpaper, but I would fully dismantle all of the parts first: Sanding creates dust, and you don't want it getting into the MAF sampling tube, IAC port, sensors, etc.