What's happening to the coating on the OUTSIDE of my roommate's non-stick cookware as we wash it?
Are you SURE they were advertised as dishwasher safe? If so, contact the manufacturer because they were lying. It is, in fact, the bare metal you're looking at— those pans are made from aluminum which was anodized: an electrochemical process which changes the appearance of the metal. All aluminum pans including anodized ones that are not painted or otherwise coated will be damaged in the dishwasher because aluminum is sensitive to strongly alkaline chemicals, and dishwashing detergents are strongly alkaline. As long as the interiors have some sort of coating, such as Teflon or ceramic, the exteriors of the pans should work fine, but they'll never look quite as nice as they did. If the interiors of the pans aren't coated, you might want to consider seasoning them like you would a cast iron pan to avoid eating a bunch of aluminum that was softened in the dishwasher.