Horror Stories indeed. I personally use POR15, into a project right now that it is being used on, and the major criteria for using it is that the metal surface is, to some degree, rusty. Not to the extent of having huge rusticles and pieces of plate rust falling off at the lightest touch but rust has to be present for the POR15 to bond to. That is not to say it won't bond to bare metal, but new metal has to be grease and oil free before it can be applied and get some degree of success and it won't go over a coating like EDP; nothing to bite into.
Since I am almost in a perennial death match with rust. how I personally generally go about working with POR15 is to use whatever methods work best to remove as much overburden as possible. Then I use a wire wheel or coarse stripping wheel to get down to bare metal. The pits and acne can be too deep so some judgement has to occur on how far to go with the surface prep. Then I apply a layer of Rust Mort, which is a rust neutralizer. You can tell if it has worked when the metal turns black/grey in areas where some rust has remained. Too much surface rust and it won't change color so that tells you more metal prep is necessary. Just did the rad cradle in my S-10, posted elsewhere, and it took multiple passes with an air drill fitted with various wire wheels to dig into the crevices and seams and get them willing to accept the MORT.
After that came a coat of the POR15 and another will get applied tomorrow. They do get along, as one is a neutralizer and the other is an encapsulator. The difference being that encapsulation does not eat the rust out or kill it, it only isolates the rust from accessing the oxygen it needs to keep the process of oxidation going.
For myself, the final layer will be a couple of coats of Flat Black Krylon Anti-Rust. POR15 is U-V sensitive and even when cured is soft enough to be damaged by abrasion. So it gets a top coat of paint as a defense against damage. Why Krylon? Location, location, location. The rad cradle is mostly buried behind the grille, bumper and lower fascia. The factory color was black, so back to black it shall go.
If you do go the POR15 route, follow the instructions and either use clothes about to be tossed out and burnt, or hit the big box hardware store and get a cheap pair of painter's tyvek coveralls. Do be aware that POR15 can soak through cloth and coverings if they get soaked or you lay in the stuff by accident. Beware the fine print on the can, once POR15 dries on skin, no regular method of removal will take it off. Only two methods that will work are time, and sandpaper (or a 4.5 mini grinder) Not even greasy chicken fat, which will remove almost everything, will make much of dent in the stuff. There is a solvent sold as a thinner for if you want to gun shoot the stuff but have never really worked with it so can't say.
Nick
