I've used Rustoleum rusty metal primer on some small parts, topcoated per instructions with their semi-gloss black. I've found lately that combination isn't very durable and scratches easily. I painted the road draft tube with it and it has already been chipped from being in the box waiting to be installed. It can be touched up, but I've found that epoxy primer with the same topcoat is a lot tougher and scratch resistant. Just an observation.
