dunno about the ernie balls, but elixirs have a coating on them (called Nanoweb or Polyweb) that slows the rusting. and it does work. i've had a set on my strat for a few months now and there isn't a single speck of visible rust on it. the thing is that the string might feel a bit weird, like you can feel the coating, and it can feel slightly plastic-y. but if you can get used to it, they're great. some people can't though. they're also relatively expensive compared to normal strings.