You're supposed to apply Por15 to rusted metal, not bare metal.
If you have clean bare metal you can get POR-15's etching product to season it. It comes in a spray bottle, they also have a pretty wicked degreaser.
Basically it doesn't have to be rusted, it just needs something to grab onto, even rough sanding the area should be enough. That's what they tell you to do between coats anyhow.









