They look to be stainless, but before I ruin them by trying to clean off oxidation and crud with the wrong thing, I figured I'll ask.... If they are stainless (they appear to be an unfinished metal of some sort with a slight "grain" machined or polished into them circumferentially) what material can I use? Some kind of ScotchBrite pad, 1500-grit wetsand paper, steel wool??? I got a set used for a good price, but they just look a little "skanky" so I'd like to make them more presentable before bolting them in. .