Also, is the rust in the binding inserts that you want to use? If so, can you work it out by bolting/unbolting a few times?
Honestly, if it's positions you'll never use I'd just clean it, wd-40 it, and not worry. You'll replace the board before the rust will do any damage to the board itself. (Unless you're planning on re-selling it someday?)
If it's positions you need and you can't clean it out, the board is a doorstop and should be returned asap.