[targa80]

I might be wrong but primers will not protect the metal finish from rust for any extended period of time. From what I have read about primers it is suggested that paint be shot as soon as possible. primers are porus and must be sealed with paint to prevent moisture and contaminants from getting to the metal and causing rust and paint lift (pealing) over time. Etching the metal will only protect the metal for a short period of time also (several days) and requires primer and paint ASAP. Sealing the metal with a product like POR-15 or equivelant product will protect the metal for a very long time period from moisture and rust. It would be best to shoot a layer of primer while the POR-15 is still curing to create a bond between the two. Otherwise you would have to sand the por-15 before priming at a later date. The primer will also require light sanding before painting if you leave it unpainted for more than several days. Sanding the primer would be much easier than sanding the POR-15.

I sprayed my tub with POR-15 and coated it with primer 45 minutes after the second coat of Por-15. The next day I lightly sanded the primer to remove imperfections and then shot the base and clear coat. I feel very confident that my car will not rust in the future with the POR-15 coating. Like anything else only time will tell.