Need advice rust on the frame?

It depends if it's surface rust or does it have cancer? If it's just surface rust then you can take a wire wheel to it then chemically treat it with a rust kill. Then I would wipe it down with acetone and proceed to primer and paint it. If it's a larger area then sandblasting would be the easiest.

 

Unless you're wanting to show off your truck, if it's just surface rust, I'd use a wire wheel on a drill or a wire brush, knock it off and use Rustoleum or a similar rust preventative paint and spray it. Once it's done, you'll be happy with the results, and it won't take more than a day to do it.
But, if having a show quality paint job is what you want, then do it right. I'd suggest doing it as I said first on one side of the truck, and see how you like it. It won't be expensive, and if you don't like how it looks, when you sand blast it it will remove what you did, and you'll only be out a few bucks.

 

I've been hearing good things about a product called Chassis Saver from Magnet Paints, but only from people putting it on car frames in northern climates. Not sure how it would hold up on truck frame, but I plan on trying it. here's a link to their website http://www.magnetpaints.com/underbody.asp

 

I used the "Chassis Saver" on the frame of my 1955 chevy truck and although it doesn't run up and down the road under all conditions, after 4 years it still looks good and is not bushing up or flaking off.

 

POR-15 will be your new friend. It takes care of rust and it is thick. You can brush it on or spray it and a little bit goes a long way. We used 1 quart and did the entire frame of an old 70's model chevy plus the inner fenders and firewall. It's about $150 for a gallon around here. http://www.por15.com/

 

Buy a quart from NAPA. Its the best product going. There is no equivalent. Don't get any on you it doesn't come off easy.

 

Friend of mine used that on the frame of his Peterbilt, most of it is already gone and the frame is all rusty again, it didn't even last two years. He used a wire wheel in an angle grinder and knocked off anything that was loose, then wiped the entire frame down with paint prep and brushed the POR-15 on.

These products may work well in the automotive side of things, and that is who they market their product to. They just don't hold up to the environment that our trucks go thru. I still think the best thing to do is sand blast the frame, apply a GOOD quality primer, then a sealer, then two to three coats of paint. Doing it this way should outlast any factory paint job by a long shot.

 

I second this, POR-15 is probably the best stuff on the planet to stop, combat rust.

 

Let it by known that POR-15 doesn't work well if it gets a lot of direct sunlight... Just paint over the top of it and all is well. I'm guessing your friend didn't do this, I too have had friends use this product on big trucks with paint without a problem... Heck, the frame will probably break before it will rust using this,(POR-15) and a quality paint over the top. Of course, underneath a car or pickup wouldn't require the paint as it's not in direct sunlight.

AS others have said, there isn't anything on the market that even comes close to this product.