It depends on the scratches and the original finish of the cans. Some have a brushed finish, some are sort of polished, some are just bare Ti. You can file the big scratches out, I've got several different files, starting with a mill bastard, working through a second cut, then a mill smooth, then sand paper, coarser at first, a bit smoother, then smooth, finally, I use scotchbrite, purple, which is a fairly aggressive cut, but can leave a nice finish, at least a consistent finish. It takes a bit of elbow grease, and a bit of experimentation, but you can make it look acceptable. Sometimes you have to grain the other side to make them match. Or you can drill out the rivets and get a new one from the manufacturer.