Saw the thread about the lower rear door rust issue a couple months back and had this repair on my to-do list.

My '08 had a bit of the rust bubbles last fall and this spring the paint flaked off in a couple areas.

Today a stripped the paint down and found a couple things on my rig that may answer some questions from the original thread:

-The rust issue seemed to be pretty superficial in nature. By this I mean it wasn't coming from inside the door itself and doesn't seem to be compromising the fold of the inner seam.

-The rust seemed to be arising from the lack of sufficient e-coat and paint on the top edge of the seam but doesn't seem to penetrate down into the overlap.

-Any smaller bubbles around the seam were indeed the rust fanning out from the edge of the seam. As you strip away the paint you can see exactly where the corrosion extends to.

I stripped all the paint away with a fine wire wheel and then took out the deeper pitting in areas where the rust was a bit worse using a courser wire wheel. Once cleaned off, no further corrosion of the seam itself was found. Usually if rust is originating from within the inner seam, after you strip the area down the seam will have a layered, flaking appearance. Mine did not.
A wire wheel on a Dremel or drill will prep the area easily. Make sure you remove all the paint to just past the area of any corrosion. You can easily see the darker discoloration of the metal from corrosion as you strip.

I then cleaned the surface with some refinishing degreaser and applied two coats of Rust Bullet with four hours between coats as suggested.
I'll top coat it later when it's fully cured. You can leave the RB as-is if you don't want to top coat. It is extrmemely durable as a topcoat itself.

I've used both POR and Rust Bullet in the past (the only two products I feel worthy of actually keeping rust at bay over the long haul) and I prefer Rust bullet over POR-15 for a couple reasons. First, RB is an aluminum particulate finish and this type of finish bonds to the metal surface much better and easier than POR thus no acid etch is neccesary. Scond, POR is more of a 'shell' whereas the Rust Bullet forms more of a matrix with any residual corrosion.

In any case, I'd like to thank all here that posted up the original thread and got me to check out this inconspicuous area to begin with.

If you haven't taken the time to touch up the area, I'd suggest you check it out. If you are DIY'er, it's an easy hour or two job.

 

Pretty bold statement. With rust there"s nothing permanent except metal replacement. But,lets see it in Nov. Or next June,17.

 

Point well taken. I meant permanent as in the finish adhering to the surface applied to. All visible rust was removed.
Time will tell if any rust remains in the fold. I'll update this fall and again after winter.

 

Nice job Xlr8n. I'll get to mine before winter. Adding the bottom of the door to regular hand washing also helps over the long run.










I hear if you wipe the seam with Techron, then Seafom, before paint, the repair lasts twice as long and you get better MPG?

 

Touche'! lol

Yeah, I wipe them down regularly as well. Same body seal as the fronts, but for some reason the fronts have no issues with rust like the back. Weird problem for sure.

Let me tell you, I absolutely hated the thought of taking a wire wheel to the paint of a newer high dollar vehicle like this (even if it was a bottom inner surface that is hardly seen), but it was obvious the rust would make it's way to the bottom edge of the door and eventually around to the front side if it was left as-is.
After finding out how much corrosion was actually hiding under there, I'm glad I didn't wait any longer.

 

I just noticed a little paint bubble on my 2010 at the inner seam on the rear passenger door. I have kept mine clean around the doors since new so I suspect it is just a prep issue in that area. It's time to dig around the bubble and see what I find.

 

That made me laugh.

Good work XLR8N