Update:
I found this stuff called "Everbright". It's a self-levelling protective coating for all bare metals. It can be wiped on, sprayed on, or the part being coated can be dipped.
It's pricey ($26 for a 13-oz aerosol can), but it looks like it's suitable for the task at hand.
Here's a link to their website:
http://www.everbrite.net/