I found an aluminum bike in the trash and it seems like it has been exposed to the rain, especially because some of the metal is slightly rusty.
The frame is a different thing, because altough it is made in aluminum, it has worm-like bright shapes, with a small relief (when I pass my fingers it isn't as smooth as the rest of the frame).
So, my questions:
Is this "rust"? (I know aluminum doesn't have corrosion like steel does, but this is IMO somekind of corrosion).
Is this a damaged in a point that it is dangerous to use it again?
Can I solve it? (I tried sanding a small bit and it takes care of it, of course the shine is gone in those bits).