I dinged my passenger side door bad enough that I went and picked up a replacement door from the local junk yard. Overall the replacement door is in great shape, but the bottom seam on the interior has a significant rust issue (see pics below). My thoughts are to clean up the rust as much as possible with a wire brush and grinder, get it as clean as possible and then apply a couple coats of a rust converter (inside and out). Since a lot outer panel that was folded over has rusted away, I was thinking to use some metal bonding adhesive to join the inner and outer panels together. Once all of that is done, a little bit of body filler to smooth things out and then paint.

Does this seem like a reasonable course of action? Thoughts/constructive comments/advice is welcome!

 

The outside of the door panel only has some minor rust showing.

 

I did pretty much the same repair on my doors a few months ago.

When I was asking questions on some autobody forums they were all laughing at me because it would be a waste of time.

I went ahead and did what you're planning. Wire brush, grinder, etc., rust converter, prime, paint. (I took the extra step of using seam sealer to blend in some of the worst area of the door)

They were right.

Wasn't much more than a couple months later that the rust started to bleed through in spots.

There's just no good way to clean the inside of the door unless you chemically dip it.

 

That's funny, I was literally thinking of doing just that right when I saw the notification of your post! Since it's on the very bottom of the door, I can put an inch of a chemical rust remover into long, narrow plastic bin that I have and let the door soak for however long is needed. I guess now I need to sift through all of the BS products on the web to find something that actually works.

 

I live where they salt the roads in the winter and I'm constantly dealing with rust. I have been trying to find a magic product that actually works as advertised but they've all fallen short.

Best results I had lasted about 2 years. That was POR15 on a Dodge Ram frame.

I don't know what kind of chemicals they use where they dunk whole cars but I have seen great results with that process. Not sure if that's a DIY version of that.

You might also want to look into electrolysis.

I don't have personal experience but that's supposed to work well and can be done at home.

 

I would just take the door back and get one without rust .

 

You must live in the South

Finding rust free doors in particular the bottom seam is next to impossible pretty much anywhere there's winter.

 

Rust converter is ok, but I would suggest using phosporic acid to chew out the rust. Works excellent. Easily found in the home improvement stores as concrete etching agent, a gallon costs about 17. Get a gallon chemical sprayer or use a spray bottle but get the area nice and wet and keep it like that for an hour (respray as needed to keep it wet and working). Then rinse it off good and dry it with a hair dryer or a leaf blower, once dry paint it with an encapsulating paint (chassis saver, por15, kbs, rust bullet) and keep going up, cover the bottom 4" or so of the inside panel. Do a job nice and paint it twice. Outside your going to have to sand the 1st inch or so of the door and prime it with a good etching primer, no spray bombs. Then just the paint the whole thing.

 

I live in Pennsylvania...I'd have a better chance of finding a winning lottery ticket!

 

Yeah, like I said above, it occurred to me that it would be pretty easy to soak the door in a rust remover since it's just the bottom edge. Phosphoric acid is probably a pretty good choice since it's inexpensive and thin enough to get between the inner and outer door panels. I'm thinking I'd pour some into the inside of the door every few minutes just to keep 'fresh' phosphoric acid working on clearing out the rust where the inner and outer panels are against each other.

After rinsing the door with water, I'd want to make sure I get all the water out, so I'd use my air compressor to blow it as dry as possible and then apply a liberal coating of WD-40 inside and out and then let it sit in the sun for a while. Once that is done blow it with the air compressor once more and spray the inside and outside with brake cleaner to remove all traces of WD-40. I'd then apply an impact resistant structural adhesive to the inside of the door along the bottom seam, trying to force as much adhesive between the panels as possible. After that cures, apply body filler as needed, sand smooth and then paint. Once everything is done, I was thinking applying some undercoating like Surface Shield to the inside of the door probably wouldn't hurt.

 

I second the use of a oil undercoating of some sort (Fluid Film, Woolwax, NH Oil Undercoating, Surface Shield, etc) inside the door after acid treatment, primer and paint. All of my trucks since 2004 have been well coated and it has significantly halted the rust. I wouldn't say it stopped the rust entirely, but slowed it to a crawl.