You refer to the crap that turns iron oxide to zinc oxide? We used that on a Studebaker restoration years ago, the longer it sat the harder it got, the painter were ready to shoot us for ever putting it on. Good stuff if you don't need a finished look. No, it's not POR-15, that has a harder enamel-like shell that can only be defeated by nukes, brakefluid and years of sunlight, afaik.
I'm trying to decide if some of the stick-on rubberized type stuff is better or worse in the long-term than a spray/roll on type applicant. I have NO rust or even worn paint right now, and I'd like to keep it that way, as well as make the cabin a little quieter.