I got the studded tires out of the basement to put them on my spare wheels, when I saw a few of the studs had turned to rust. would they still be any good (until they get completely rusted away)? Also are the studs generally resistant to rusting, or is there any solvent or anything I could do to prevent further rusting? BTW they're Nokian 291??'s I belive, 3 years old, but I didn't use them at all last year.