Q&A for How to Clean Oxidized Aluminum

Yes, first of all I would try wiping it clean with white vinegar. But if that does not work, I'd try lightly sanding it with sandpaper or scrubbing with baking-soda and water mixture.

It depends what the item is doing for you; if it's a decorative piece that has a finish over it you can dimple down the area and repair it for appearance with a body filler. If you need a structural repair you'd typically need to replace the item unless it's expensive. You can have holes ground out and aluminum welded and ground to resurface, but that's typically not worth the cost.

Corrosion from acidic cleaners or scratching from abrasive cleaners is damage and cannot be cleaned off.

Try to work a smaller surface at a time, like just the door, with the same general principle: wash, scrub, clean, polish and wax. Since it is a vehicle, and you probably intend to use it, you may want to go to a mechanic.

OxyClean and a soft brush. It may take a few applications. Mine were pretty bad from the dishwasher.

Lemon juice and bicarbonate of soda work well. Paint it on, leave to work and wash/scrub off.