I was given a case of 20 gauge shells that were in a house that flooded. The shells were not underwater, but the hot humid air caused them to rust. They were 10-15 years old before the flood and have been sitting in there rusted state for another 5. I would say 25% of the brass has a rusted surface, mostly on the side and very little on the bottom by the primer. Polishing up with some 0000 steel wool cleans them up well but some have lost metal at the lip. I cut one of the worst ones open and the pellets poured out easily. The powder burned and the primer popped when struck. I think these shells are usable. Any experience here to say otherwise?