Somebody please correct me if I'm mistaken... I thought "Armstrong" (Elswick Ordnance) studded projectiles only had copperbrass studs -- not have zinc/white-metal studs.
Ozarkeod, you asked about what to coat zinc studs with. First, remove all concretion/corrosion from the zinc (but save the "patina"), then apply several coats of Polyurethane (satin-finish).
Regards,
pete