I have used POR-15 on several vehicles. It works very well on rusted surfaces but it does not adhear to clean metal all that well? I have had several places peel after a while using it on clean metal - even using the metal prep. It will stick better to clean metal if you can wet the metal then wipe the water off and paint it while the surface just has a hint of moisture left on it.
What ever you do - do not breathe the por-15 fumes. If you do you could very likely never be able to work with paint again. I had a leaky air supply line and got some into it - I will never use the product again, not even to brush it on!!!
I have started using the Rust Bullet. It works as well but is not as harmful if you breathe some.

Scott...