I've got some weight plates that need painting, they are quite rusty. Made of good ol' iron.

I was going to clean off the rust and paint with Hammerite, but I hear that it might not stick very well. Should I leave some rust for it to stick to? Should I use a primer? Will it stick to an arcanol based paint/primer?

Any suggestions would be nice. I'm looking for a strong finish that can take a beating.