Sealer is good for seams that have already been galvinized or treated with epoxy primer, encapsulator, or a self-etching primer. Otherwise you are capsulating the moisture with the sealer.
Me personally, I would clean the area good, then hit it the bare steel with a self etching primer (zinc will inpregnate/etch itself into the bare steel), then epoxy primer (PPG, Southern Polymers, etc.) for durability, then I would hit it with a buildable primer (perform bodywork), then base then clear. etc.
short term (less then a year inside ONLY) self etch primer (green preffered) dont put it on very thick, it should be almost transparent if appled correctly (2 coats)