volfy,
Please digress. This sure beats the Campy vs. Shimano threads.
I was going to say epoxy primer. My auto parts store carries it. Works great on steel, and even better for aluminum when regular primers don't like to stick. There is also a new one by 3M that supposedly oxidizes the metal when applied, and also acts as a color coat adhesive layer. Sort of a 2 for 1 deal, to make prep from bare metal easier, and is apparently much less toxic than an actual bluing agent. Some of those salts are pretty nasty stuff.