I used POR-15 on a few areas of my project. It hasn't been on there long enough for to attest to its longevity. What's nice is you can brush it on.
Be sure to get the POR-15 lid and sealing area spotlessly clean before you re-seal the can. Otherwise, the lid will be fused to the can. Ask me how I know.
I thought I had the lid and can clean enough before I re-sealed the it. But I guess there was just enough residue to glue the lid to the can.
FYI, you have to topcoat POR-15. UV light breaks it down.