yes once you replace them they're going to rust again. you're better off painting the whole caliper assembly to prevent rusting. I don't know why BMW did not do this as I've seen brand new cars on the lot with rust on the calipers already? if you're not looking for anything that stands out there's quite a few members who painted their calipers black and silver. for me I did mine gold only to blend with my wheels. but after a few years the paint is still holding up and no RUST!
