Ok guys, here is the scenareo. I have a 1990 F350 XLT Lariet extended cab DRW with less than 100K miles. Truck is in extremely nice condition, never wrecked, abused or even worked hard as a truck.
Problem: There are small spots of rust showing up under the original white paint which is very thin. No, the rust spots are not coming through from the backside of the sheetmetal. I've just left the truck go too long with thin paint.
Question: I will probably have it painted and want to know what it will take to kill the rust so it is not back again. I want to be able to talk to the paint shop with some indication of what it needs as opposed to taking it in and saying, "paint it".
Will etch primer kill the rust?
thank,
ray

 

There are products that when applied to the rust spots, once the paint and rust has been ground away to bare, clean metal, these products will treat the rust and bring them to an inert black rust, then sealer, then primer, then paint on top. That should work to hold the rust at bay. Only thing depending on how deep the rust has eaten through the metal, filler etc will have to be used first in order to create the smooth surface to seal, primer and paint. If the rust has eaten through the metal, then it's best to cut out the rusted area and weld in new panels. Good luck!!

 

I have the same truck, they are NICE, I really like mine. Those extended cabs are the BEST!

I also had the same problem, nice truck but rust spots all over the hood. So many the I decided the sand blast the hood back to bare metal. The front of the roof and only about a dozen spots, so I just treated them as follows:

Find EVERY spot that has rust. Sand down the full area around it as there could be some hidden. After you feel all the rust is showing and sanded with about 80/60 grit. Pict at the rust to insure it's all gone and you truely have pure metal. Buy some metal prep (phosphoric acid) from home depot for $8. It's a watery lime green liquid and comes in qts. Buy some acetone and gloves and paper towels and a brush.

Clean the heck out of the whole area with acetone and paper towels. Allow to dry 20 min. Apply with brush / spray the phosphoric acid (clean up the drips) allow to dry for 1 hr, re apply making sure the full area of rust is covered.

allow to dry 1 or 2 days until flakey/ dusty. scuff with 500 grit pad or wire brush. remove all the dust / white powder / black flakes... then clean several times with acetone and paper towels.

You should have a grey looking metal, it's now ready for final clean and primer.

Notice that this will NOT hold up to weather without the primer, so don't delay too long. If it turns rusty again, repeat. (even cheap primer with work till you get it to the shop).