if the whole thing is well treated with phosphoric acid [Ospho as CASO says], epoxy will work, the trick is to make sure all the pinch welds are flushed out well so no stripper chem bleeds out under the primer - but you shouldn't count on doing your welding after epoxy unless you're also prepared to strip the epoxy off the area to be worked
Bill
Check the data sheet for your epoxy primer. Some of them have adhesion problems if used over phos acid.
