I was stripping my car getting it ready for a paint job, and on the upper quarter panels near the top part of the hatch, or on the back side of the window, there's these little black spots that can be sanded away but come back in about 5 minutes. i know i'm not burning the metal so that's not it. is this rust underneath poking through? the body guy says he wants a new panel. so what exactly are they? and also some other body guy said GM cars were famous for having a black "shadow" that spreads across a panel then the panel falls off, and he wasn't kidding....WTH?!

 

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