I'm on the same page as Alvin,although I didn't need my chassis blasted (it didn't need it),there was more caked on dust and grease than rust with a fair bit of the original factory finish still left on it.
I went down the POR-15 route.
I've basically painted the whole chassis,the underside and inside of the cab and under all four fenders
I know the basic concept of POR-15 is 'paint over rust' but so far it's holding out just fine and the dirt washes off easily.
Just as well as i'm in cattle country,it's not just mud....
Nothing wrong with painting POR-15 over clean, sand blasted metal as a primer. I have done motorcycle frames this way. The only downfall is that it is almost impossible to remove! It laughs at sand blasting and paint strippers. Some people have the misconception that you can only paint it over rusty metal. Not true. It sticks very well, even better, on sand blasted surfaces. I have been using it as a primer for years and have never had a problem of it coming off.
