As jomichael posted, POR-15 is supposed to be used over rusty metal (after removing paint and any loose "material") or a special prep is needed with clean metal.
If you are getting the framed blasted, you might want to just spray the clean metal with epoxy primer. That will seal the metal. I used a black PPG DP90LF/DP90LV epoxy primer. Then you can decide if you want a finish coat or just leave it in primer.
