Rustproofing

[ShadowsPapa]

Copied from above...

I spoke with my dealership here in Iowa and also contacted a guy in Technical at Fluid Film. He was very willing to listen and go back and forth about FF and undercoating pros and cons to each. After hearing my whole story/situation, I finally asked him what he would do at the end. He said to put it plain and simple, do the undercoating at the dealership. It will be put on without being on the road and the truck will never have a better surface to protect after that. He also went on to state that I should use FF on suspension components and everywhere the undercoating was not. He said if I spray the undercoating, it will soften it and it will come off. As soon as the undercoating starts to chip and come off on its own, he said to apply FF annually all over the underside of the truck. There's also a great video on their website that shows applying FF to a truck as well. Hope this helps you guys, I know it helped me decide!

WOW that guy was honest as heck. Cool.
I've really never had original type undercoating flake or come off on its own in less than about 9 or 10 years. In fact, the dealer stuff on my 70 Javelin was mostly intact when I restored all the suspension and steering back in 2007 or so. That's almost 40 years. The undercoating on my Eagle (1982) was almost all intact in 2012 when I nailed a deer and ended up repainting the car.
But I agree on the suspension parts like the links and arms and things you don't want to rust but that they won't (or should not) undercoat.
They sound like a decent company with honest advice like that.

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[TRRalpha]

I used LP3 on the underside /frame including inside the rails. I used FF on any interior panels such as inside doors ,hood ,tailgate and rockers. Theory being FF does wash off at some point and needs annual to semi annual reapplication , LP3 is not coming off. I'v had FF on my FJ since it had 3500 miles on it and it shows no rust issues at all . On a side note the FF also acts as a lubricant for window regulators and lock/ linkages verses the LP3 is just a corrosion preventative.