Okay guys, well, I have the Barracuda flipped upside down and my 7 year old son and I descaled the underside of the car and have taken all the undercoating off. That is the good news. The bad news is these frame rails have a lot of rust in them. I will end up putting caps over 3 of the rails as 2 of them are toast, but before I do, I want to treat the rails. So, what do you guys use to treat the inside of the frame rail and what are your techniques?

I,d forgot about trying to clean and paint the insides of the rails with any type of rust convertor and or paint.

It,s just about impossible to properly prep and apply any type of paint on to all those enclosed nasty scaly rails and freshly welded joints and have it last. ( Short of diping the whole thing etc. $$$)

I,d just spray the crap out of it after your done with the metal work with something like this .
http://www.corrosionx.com/hd.html

Use a windex spary bottle with "ospho" which is phosprhoric acid. It kills rust and you can get it at most hardware stores pretty cheap. Turns the rust black and it stops it from getting any worse. It won't eat up the metal cause it's not that kind of acid.

I had forgot I have a couple of bottles of OSPHO already. I suppose that would do the trick. I probably need to look around and see where I can get some hose and a sprayer to apply it. I have the caps that are going on top, just figured I would want to stop the rust that is already there. Looked at some of the rust disolvers, but they pretty much require total immersion, or setting some sort of system up that can capture the liquid and then pump it back in. Of course, the problem would be the liquid does not need to be pumped in, it needs to be sprayed in to get complete coverage. I don't think my car is an isolated instance, the frame looked good on the outside but once the needle scaler broke through, there were huge chunks of rust at least 1/8" thick. Weird think about it was everywhere there was undercoating the car was good so I thought no problem. The one rail that was coated the heaviest was the worse one of all.

I'd use a garden sprayer. The pressure will ensure it hits every square inch and the wand will let you get in a good distance from the various access holes. I'd have to say that you probably can't use enough of this stuff in there!

The sprayers are cheap at ACE Hardware.

Use SEM RUSTMORT. Also contains the acid, but dries much harder. Forget the frame rail caps. Find a good doner part.See pic. Caps are for a quick fix!

once ospho is applied,repairs are done and painted, i would spray oil inside of frame rails to prevent rust.

Hey, I know someone with some donor cars with good rails... hint - hint... LOL

A couple more ideas I've not yet tried. There are some body cavity waxes made today. These are being used by some auto manufacturers (volkswagon?)on new cars to increase rust resistance.

I've also heard that some guys use a water proof, non-shrinking foam to fill places like this. I'm not sure how or if this would affect the car in an accident.

Hopefully, someone who knows more about these ideas can comment.

in areas of the world woith lots of salt on the road (for example Germany...) we use this wax or grease like stuff in frame rails. Not sure if available in the States, but I had GREAT experience with "Mike Sander's Korrosionsschutzfett". Essentially it is a grease which you heat up until it gets liquid (almost like water), then spray it in with a 360 degree nozzle. When the sun burns on the car it starts to melt again and digs into any rust which has redeveloped.
essentially you deepfry your car...

The best enclosed cavities rust the first. You need to get the water out of frame rails! It will always find a way in (air moisture if nothing else...), if there is no way out and no wax / grease to poush it away you get rust.
damhik...
Flo

I would take a sanblaster and spray it in all the areas you can acess thru holes and openings. Also i woud,nt cap the rails, i would remove and replace at least the worst areas. good luck

i used 90 wayt oil but know I coulnt git it aull

I like the idea of a grease that is applied hot (thin) and solidifies when cool.

Use a rustproofing gun to get all the nooks and crannies.

don't use POR15. that stuff would peel off in sheets within a short matter of time. its also expensive.

I know this is a really old post but I need to treat the frame rails on a couple of cars and wondering if there's any better ideas/products on the market now to deal with this issue. I have the floor pans removed on my cars so it's easy to get inside the rails except for the front rails inside the engine bay. Also need to treat the inside of the rockers.

There doesn't seem to be a lot of good opinions of POR-15 judging from the earlier posts. I also remember a member on here several years back that was trying to develop a spray rig to get POR-15 inside the frame rails and other inaccessible areas.

So what are you all doing to treat yours?

Jim

this will do it .... http://www.flywheeldistribution.com/cosmoline-rust-veto-quick-dry-rust-preventative-aerosols/ if you want it finished with paint , use etching chromate primer first...

Hot Rod Mag , did a write up about all the rust remover's a while back.
one thing that they did was make a recirculating system with a homemade trough and plastic sheeting to direct it back to the trough with a pump in the bottom .
the fluid was then allowed to spray out of a home made pvc spray bar for a few hours and the rust was removed clean.
If i had to do it i would try this approach.
also i have real world experience with P0R -15
most of the problems people have is they don't read directions.
por-15 will peel off off clean unsanded or sand blasted metal if not treated with their version of ospho called Metal Ready ,
if you follow directions it is like powder coating hard!I have it on many projects. por also adheres to rusty metal not clean metal or untreated with metal ready. IT practically self crawls to cling to surface rust.
that said if the rails are cleaned to bare metal clean i would chose to use Dupont Variprime self etch primer sprayed in with garden sprayer .
Cj