Ugly Duck wrote:
Picture the box channels that make up the "frame" of the car: how are you going to get inside there to protect that with a Shutz gun? You need a flexible wand with a 360* mist tip to get everywhere you need, and you need something pretty thin to flow through that.
The only thing I know that WORKS, aside from hot dip galvanizing, is an annual oil bath. It's messy, though.
The stuff I used was specifically an undercoating, but it did dry like a rocker gaurd - we'll see how it holds up, but I've got no reason to suspect that it won't. You will need a flexible wand to get into all the areas and seal it up, that's how the pro's do it. If you drive the car, there is no real substitute for undercoating. The Ultra Shutz was like water, so it should work for spraying into tight areas. As long as you can't get water into an area easily, then you don't have to worry - use sprayable body wax (3M again) if you're unsure.
I've used POR-15 on my suspension and it shines and cleans up great after 2 years of use - powdercoat in a can. It (or something like it - water cured polyurethane) is the only way to do this cheap, and it is still 5 times the cost of undercoat. When I did my inner fender repair, I used POR on the inside of the box sections (they are 3 feet long) tape a brush to the end of a coat hanger and give it a good couple of coats - should last longer than the factory part (lasted 41 years) and had nothing inside.
My problem with the oil bath is that it is environmental terrorism - let's not be putting our used oil anywhere other than the recyclers. If you have to spend some money getting it done right, spend the cash. If your car is that important, and honestly they made lots, and rust repair isn't that hard, get it done correctly.