We had a fire in our living room at our old house in 1996. It was out in a few minutes, but the whole house was really smoked bad with the couch, loveseat and carpet all melting/burning. I had several long guns in a rack that all got smoked. The smoke from all of the burning materials was very acidic and pitted the metal on a couple shotguns and a rifle. My stainless mini-30 darkened a little, but it fared the best. I eventually stripped and sanded the barrel on one shotgun and put a Cerakote finish on it. It's certainly not back to any original condition, but it looks much better than it did, and it shoots fine. It was a used double-barrel that I got as a teenager, so it's sticking around the family some more. Cleaning them immediately kept them from being worse off.