There's a small tapped hole on the outside top of them that was rusting on mine. I sprayed some black paint on a Q-tip and dabbed it in the hole to cover it up. That's the only place that has rusted though.
Mine have both had surface rust on them along with some other areas as well. I took some sandpaper to those affected areas and repainted them with Rustoleum paint. Living in the northeast lends itself to moisture. I now, as part of my winter storage, cover the entire bike with a layer of wax. I do not buff it off. I leave it on let it haze up and then cover the bike. Been doing that for a few years now and have not seen any rust since. Come the warm weather I simply buff the wax off and I'm ready to go.