rust is a ferrous metal term, basically if it has iron in it, then it has the potential to rust.
when speaking about metals it better to use the term oxidisation, as this is what happens when the bare metal reacts with oxygen in the air.
in the case of a steel its ironoxide, with aluminium its aluminiumoxide.
ally doesn't oxidise easily and it would be harder to get perferation in it.
as for good will gesture from nissan, good luck, i've tried with something else, and they were tighter than a gnats ar$e. its difficult to get anyhting out of them, once out of warrenty they couldn't give a to$$. i hate nissan for that fact and delibertly don't use their garages for anything, call it a mini protest.