Technical Por15 over ospho?

Im not a fan of POR15, followed all prep and have had it fail on me multiple times.

Inner panels on painted complete cars - i shoot danish oil into the cavity with a shutz gun and an extended flex tip. Use whatever access hole you can or dril one and plug it. Danish oil is similar to linseed oil, just a blend for furniture finish, drying oil that leaves a hard oil film.

Inner panels on cars that are being restored - thin your favorite direct to metal primer way down and shoot into the cavity with a shutz gun, let it drain out.

Anything that can be accessed regularly, blast or wire wheel all rust and acid etch to kill the rust.

I no longer have any faith in rust converter paints.

Ive purchased 2 brands of "body cavity" guns with long wand tips. Neither worked well, the pickup tube is too small. A shutz gun is used for undercoating and bedliner, has a larger pick up tube. Put a clear long hose on the end and it will reach into cavities. Or turn up the air and it will shoot 20 feet.

 

I have purchased master coat, I am impressed with the video salt spray test.

Using it on my daily driver truck, Slowly cleaning the frame rust and painting.
We'll see how it does over the winter on the frame before I make any judgement.

 

I used POR over Ospho treatment inside my doors. Didn't need to be pretty (and it isn't) but stuck just fine. One tip is to wax the outside of your doors first so when (not if) you get some POR on the painted part of the skins you can get it to come off without wrecking the paint. I also apply FluidFilm regularly afterward as even Ospho/POR isn't going to be perfect. Get one of those long tip spray guns and once a year hose down the inside of your rockers, cowls, etc.