I have '96 F150 that has only very minor body rust, but a lot of frame rust. The gas tanks are all clear, but every spot on the frame that I can see, has rust. The rust isn't very deep, so I was thinking about coating it with POR-15. My question is - will painting the outside of the frame make much difference? Won't the frame just rust from the inside?

 

ahhh good choice well first off por 15 is very expensive paint and you have to do it right etc the preping meaning cleaning the metal then the zinc coating and then por 15 i love that stuff it is like glue its tuff stuff it is on right no oil or etc the paint combines with the rust so thats what they say and stops the reaction now keep in mind oxidation is rust how it works is it needs air to rust so that being said if the paint seals it perfectly it cant rust but as soon as air gets in it will rust again now i would put the por 15 on and then spray a rubber based undercoat so it stops water and air from getting past the piant also back in the day you were sapossed to under coat your car x amount of years but who did that now they say they use a special metal to stop it yeah dont believe it may slow it down but yeah i would use the paint but i would light sand it or wire brush it and get it completly clean i recomend there products you prob could get away without the marine clean but deff need the metal ready thats a nickle coating i belive and good luck rust is hatted through us all

Tom

 

you should always clean the rust before anything, but por15 is designed to convert the rust.. so would that zinc i believe. Essentially, if you wotn fix the frame by blasting it or wire wheeling etc, "convert the rust" then POR 15 coat it. I recommend a brush.. guys on my other board use it with a brush.. its kinda thin if i remember. (it comes in grey now btw!) it's GREAT stuff.. but you'll have a HECK of a time getting it off if you don't do it right to begin with!

Degrease it 2 or 3 times and spraying with a pressure washer (you can rent them!) before anything.. if you are converting and painting not bringing to clean metal you GOTTA work with clean metal.