Battling Lower Door Rust

'99 4.0, 150k

Is there a consensus on how best to fight this lower door rust? I have been sanding it off, repriming, repainting it a couple times a year, but it keeps coming back. Does the POR work on a spot like this? Or even something like Griot's Rust Remover/Converter product?

The rest of the Jeep is in great shape, and this is the only body panel rust.


David

Are you sure it isn't coming from the inside of the door? Those spots on the doors are a pinch seam and they're known for collecting water, salt, sand, and assorted detritus inside the door, which corrodes till tiny holes go all the way through the metal and start rusting the outer surface, at which point the paint bubbles and lifts. By now the holes in the metal should probably be visible though.

Rust is best fought by cutting around it or grinding it off (to bare metal), treated with a rust combiner like Xtend, doing whatever body shaping needs to be done, an priming with a good quality primer before the color coat.

Lower door rust on the inside lip is common, and generally requires grinding, treating, and priming. Make sure the drain holes are clear. I went as far as to unfold the seam once, scraped out the rust, treated it, folded it back, and primed it.

For more extensive repairs, just take your time to cut out the affected areas and replace with metal. Don't forget to overlap the formerly cancerous area.

kastein said:

Are you sure it isn't coming from the inside of the door? Those spots on the doors are a pinch seam and they're known for collecting water, salt, sand, and assorted detritus inside the door, which corrodes till tiny holes go all the way through the metal and start rusting the outer surface, at which point the paint bubbles and lifts. By now the holes in the metal should probably be visible though.

Click to expand...

Agree with Kastein. The door seam is where it starts and it "migrates" up the outside part of the door. Bad design.

I have used rust converter successfully to "slow down", the process, and then paint over it, but you never stop it. Rust never sleeps.