There is another thread right below this about it too. I have a 1985 f150 very little rust at all actually. Still the undercarriage is in need of some attention before anyone lets it go. I plan on sanding it down a bit. Now i saw from the thread below here that the undercoating stuff in stores flakes off after about a year or so. I plan on doing some mudding so i would really like to do something here. Would rust preventing paint work? I see it and it's about 5 dollars a can which is freekin rediculous i'm going to try to find it in bulk at BJ'S or something. I would think that paint would actually stick better then what undercoating in a can would. Does any one know where to get that paint cheaper if that would work? Thanks guys.

 

The only thing I've seen that truly works is a product called Paint Over Rust (POR). It's not cheap, but it really works. I've seen less expensive stuff, but quite honestly, you're wasting your time and money. You get what you pay for.