I originally posted this down in the bodywork forum, but it's pretty slow there. I've asked body shops in the past what to do about rust and most of them blew me off. I know why; there really isn't a fix, but I've got to do something. I'd replace the cab if I could, but it's a lot of time and $$$ I don't have right now.

I've been meaning to address potential rust for the last few years but wasn't able to get to it and whatever crap they started using on the roads in Maryland the last couple of winters really ate up the cab. I've cleaned up one side with a needle scaler and it's got some decent perforation.

I've included a couple of pictures of the affected areas. The right side (first shown) I have already scaled. Left side is unscaled.

http://www.flickr.com/photos/cmaldridge/6841528873/http://www.flickr.com/photos/cmaldridge/6841528873/ by http://www.flickr.com/people/cmaldridge/
This part that is rusted through is primarily a portion of the cab assy that is a much larger piece. I think I need to patch it.

http://www.flickr.com/photos/cmaldridge/6841526537/http://www.flickr.com/photos/cmaldridge/6841526537/ by http://www.flickr.com/people/cmaldridge/
http://www.flickr.com/photos/cmaldridge/6841523643/http://www.flickr.com/photos/cmaldridge/6841523643/ by http://www.flickr.com/people/cmaldridge/
http://www.flickr.com/photos/cmaldridge/6841522155/http://www.flickr.com/photos/cmaldridge/6841522155/ by http://www.flickr.com/people/cmaldridge/
http://www.flickr.com/photos/cmaldridge/6841519535/http://www.flickr.com/photos/cmaldridge/6841519535/ by http://www.flickr.com/people/cmaldridge/
Initially I was going to use POR-15, and I probably still will on the frame portions. I used it on the bed section of my frame and it's done really well and is very durable. However, I had tried to pretreat the seams of my new (at the time) take off bed and of course the POR-15 peeled off the already coated surfaces, and did not protect the seams which have now gotten rusty (they mean it when they say it has to be applied to bare metal).

So, on the cab I have a mixture of painted and stable surfaces and rusty surfaces. The POR-15 will do fine on the rusty surfaces, but that leaves the remaining factory coated surfaces (with just the electrocoated primer) without further protection.

I also doubt the ability to get POR-15 inside the reinforcements and rockers. Spraying POR-15 is very messy and I don't have the equipment to do so.

I have seen several "rust-converters" in my reading, Ospho, Corroseal, Picklex etc. These products seem to contain some sort of converter (phosphoric acid in most but not corroseal) with a base that dries. Some of them claim they leave a hard paint-able surface. I don't know if that is a coating that is part of product or a result of the chemical conversion process.

I'm looking for suggestions on how to best treat all of the rust, inside outside an in the seams, and seal the surface to prevent further rusting. I'm worried about getting inside the rockers and inside the cab supports.

 

Im in the same boat, my truck looks the same under the cab. Come spring time im gonna pull the bed and go to town on the cab and frame with a grinder and wire wheel. I have use por-15 before with good results so ill use it again. The most important thing is the prep, clean clean clean. Good luck.

 

i bought a cheap harbor frieght sand blaster hit it all and then acetone sprayed it when dried i too old cloths and por 15 everything and my colths were ruined after but i got allmost all nook and crannys but it still not the greatest but better than before

 

I would remove the flaky rust on surfaces you can see, and then put POR-15 on those. Then put 90wt gear oil (new or used), diluted somewhat with gasoline or mineral spirits, in a pump oil can, and squirt that into ever seam you can see under the truck until it drips out. When the 90wt oil creeps into the seams and the solvent evaporates, it will stop rust. You might powerwash the bottom of the truck first to get rid of any dirt that might be trapped in body mounts. Use caution with any flammable solvents. You can also buy several cans of spray Lithium grease, and spray that inside frame cavities and on things like brake lines. It will stick and form a rustproof grease coating.

The phosphoric acid converters must be topcoated and I'm not sure they will stop rust long-term on underbody panels that get hammered with salt and flying dirt, etc. In your case, I'm not sure they will advance your cause much.

Like all rustproofing, check your efforts 1/x year and reapply as needed. There is no such thing as a one-time rustproofing job.

 

I guess in hindsight I should have just sprayed it down with oil until I could get to it. I was afraid it would make it harder to coat. Didn't seem as long as it has been since I originally wanted to address it and seal it. But I've also had to do other body work as well in the last couple of years, so I guess it is what it is.

 

Mine is about the same. Not much you can do about it at this point.

The only way stop rust is cut it out and replace it. If you miss any it will come back. Unfortunately that isn't really feasibly without a lot time and money. Way more of both then a cab replacement. Best thing to at this point at is replace any major structural pieces that are gone, then oil spray the rest twice a year.

Also check the back wall of your cab, near the cab mounts, right where it flattens out. Mine is cracked on both sides.

 

Texaco sells buckets of rustproofing (not retail, but through a wholesaler). It's in a 40# pail, and can be sprayed or applied with a brush. Great stuff - sticks like glue and forms a self-sealing non-hardening film.

We bought some from a rustproofing shop in Michigan years ago, and I still have it. Do an internet search of 'Texaco rustproofing compound' They sell a low and a high temperature version for different climates.

 

I've done a lot of thinking about this problem.

The inner rocker panel that is picture in #1 and #3 is actually part of the A-pillar. Proper replacement would required complete dis-assembly of the cab sheet metal. I could section the bottom rusty piece of this part, but I won't get all the rust it would be a lot of messy work. Welding would invite new rust to areas that couldn't be accessed for coating. I also think I have rust forming at the back of the cab corners.

I don't know that it could ever be "right" again.

Sooo... because it really isn't that difficult for me to pull the cab, I'm considering replacing it with a cab that is in better shape. The only real problem for me is the windshield. I really need a new one anyway as this one is scratched up.

I don't see any downside. Entire skeleton cabs can be had for less than $1000, and the cabs are the same through 07. I'm keeping the truck. Removing the cab will also allow me to address the front part of the frame almost entirely. If I get really bored, I can pull the power train for complete access. I would have the entire structure sprayed red if I don't find one that is already red (which I will try ) Maybe even add some sound proofing on the inside

I will keep posted, and if so I'm sure lots of pics (which i'm sure will be helpful for proper reassembly)

 

at what point could /should u use the rust converter first vs spraying on undercoating. Its so ez and does a nice sealing job; if you want black. crinkly finish.
i have other metal beams to paid with surface rust on C beams will the undercoating seal in rust to prevent it further ?
The cost may be the same for the area covered. The converter is a sealer ; to make it ready for paint once the Rconverter is on I can paint or speay undercoating; that probably costs 3x as much

 

sounds like undercoating; rought black finish . different or not. I think if heavy rust already; I'd use converter first where the undercoat may just cover it; who knows !!

 

I've used corroseal. Its amazing at what it does but it's not a universal cure-all.

I think it's an acid based rust converter that converts red iron oxide to black iron oxide (not rust), and encapsulates it all within a primer. After 24 hour cure it's ready for painting. I've used it on my steering knuckles when I had them off 6 mo to great results. Emphasis on it being a primer; it's not meant to be used without a layer of paint.

Problem is it's brush on, and while it can work in to cracks and some holes, it works best if major rust scale is removed before application which means a needler or wire brush. Additionally, the surface must be free of grease, as with any primer.

If you not looking for paint type solution, cosmoline is the best protection you can get. It's kinda like a spray on wax... Used by militaries to preserve firearms n such. Problem is it's a major pain if you ever want to remove it.

Fluid film is good but you need to reapply every so often. A good option for complex areas where it needs to work it's way in to things.

 

Zombie thread alert! Not sure if you knew this is almost 10 years old. To answer your question, undercoating does little as far as protection. In many cases it hides it, as moisture can easily get behind it. It has its use but I would never trust it to prevent rust. I've worked on undercoated cars that looked perfect from underneath and the floorplans were all but gone.

 

Haha didn't notice the original post was ancient. Oh well