Just be aware that not all caps, and not all cappers, are created equal. All of the commercially available caps today have a bonded rubber gasket on them, so rust shouldn't be a problem at all. Not all caps will seal tightly, and not all cappers will crimp sufficiently to ensure a good, tight seal, no matter how tight you press on the levers.
If you're using beer brew equipment, make sure that you've tried it a time or two holding the pressure of carb'd beer. Lots of the dual lever cappers don't really crimp all that tightly, but all of the stand cappers seem to get excellent reviews.
If you choose to cork, ensure that the INSIDE of the neck of the bottles that you choose to use are in fact straight, and not tapered. Otherwise, the cork will only be holding at the very top. Try both 8 and 9 corks with a sample, and see which one actually gives you the best seal over a few days worth of soak time with some test water or whatever. (I recently got two cases of bottles (same as I've always used) that don't seal worth a darn with #8s, had to move up to #9s to get a whole cork seal).