Epoxy primer is designed to adhere to properly sanded …. Scratched bare metal. Sometimes you can use an acid based primer to etch the metal but sanding is best. If you have something between the metal and the epoxy, it won’t adhere properly and anything you put on top will have problems. All of your money products are on top of the primer so if the primer fails to adhere, you loose a lot…. And it looks bad.
You can use phosphoric acid to get to the hard to reach spots then sandblast but you run the risk if leaving the residue ….. just where you don’t want it.
Mechanical metal preparation by sanding, sandblasting is the best way.
Mike
