OK. A couple of points. Aluminum exposed to the atmosphere has a thin coating of aluminum oxide on the surface. So how is this different from the black spots you are seeing? Valence?
Edx was suggested as a way of detecting what the black spots are. I think edx is a shortening of edxrf. Edxrf doesn't deal with the outer valence electrons, only with electrons closer to the nucleus. So it couldn't see the difference.
Is this correct?