Cleaning rust inside the frame?

[jangell]

I did a bit more work on cleaning off my frame today, which was caked with oil gunk from the leaking engine block. This gives a good "before and after" view; some of the black areas on the right are from an undercoating I had done a decade ago when I moved from California to Vermont, and is still pretty well attached:

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I happened to look in the big machined hole on the right side and noticed a sheet of epoxy peeling off. I knocked it and various others off the inside of the frame, which of course is now inaccessible at the bottom of the frame itself (not quite sure how I'd get it out, or if I need to bother). Peeling away some epoxy from the holes I need to patch under the lower link arms left me with this pile (11mm offset wrench for scale):

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Interestingly, the flaking epoxy and rust seems to only be on the inside face of the frame that the hole is in; the opposite face is clean epoxy. I'm guessing the epoxy might not have bonded properly at the factory due to the overhanging angle, or something like that. The metal itself is solid, with no sense of it being weak or flexing or anything like that.

Anyway, I'm wondering what the best way to treat it is, without pulling the frame off the car and having it stripped. It's not terribly accessible, so I can't really reach in with tools to clean it off very well. I'm wondering if I can try to knock of whatever loose bits I can, and then get a spray wand and coat it with some rust inhibitor (POR-15 or whatnot)?

I also had a question about some cracking visible in the epoxy on the driver's side. It's not clear to me if I should find some way to remove it, or if I can just POR-15 over it.

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Some searching of the forums suggested that it might be possible to remove it with a torch (although the definition of "torch" isn't clear as yet -- MAP? Oxyacetylene?), or with chemicals (I saw that Dave from DMC MW suggest that only Redi-Strip works). I guess an angle grinder will just make a mesh and damage the metal. I also assume that I can't weld to epoxy, and that I'll have to remove it before I try to weld patches over the holes in the other parts of the frame.

The goal here is just to repair these pieces in-place, without pulling the body off and without access to a proper sandblasting system, a giant oven, or a way to submerge the frame.

Thanks!

-- Joe

[David T]

I did a bit more work on cleaning off my frame today, which was caked with oil gunk from the leaking engine block. This gives a good "before and after" view; some of the black areas on the right are from an undercoating I had done a decade ago when I moved from California to Vermont, and is still pretty well attached:

26929

I happened to look in the big machined hole on the right side and noticed a sheet of epoxy peeling off. I knocked it and various others off the inside of the frame, which of course is now inaccessible at the bottom of the frame itself (not quite sure how I'd get it out, or if I need to bother). Peeling away some epoxy from the holes I need to patch under the lower link arms left me with this pile (11mm offset wrench for scale):

26930

Interestingly, the flaking epoxy and rust seems to only be on the inside face of the frame that the hole is in; the opposite face is clean epoxy. I'm guessing the epoxy might not have bonded properly at the factory due to the overhanging angle, or something like that. The metal itself is solid, with no sense of it being weak or flexing or anything like that.

Anyway, I'm wondering what the best way to treat it is, without pulling the frame off the car and having it stripped. It's not terribly accessible, so I can't really reach in with tools to clean it off very well. I'm wondering if I can try to knock of whatever loose bits I can, and then get a spray wand and coat it with some rust inhibitor (POR-15 or whatnot)?

I also had a question about some cracking visible in the epoxy on the driver's side. It's not clear to me if I should find some way to remove it, or if I can just POR-15 over it.

2693126932

Some searching of the forums suggested that it might be possible to remove it with a torch (although the definition of "torch" isn't clear as yet -- MAP? Oxyacetylene?), or with chemicals (I saw that Dave from DMC MW suggest that only Redi-Strip works). I guess an angle grinder will just make a mesh and damage the metal. I also assume that I can't weld to epoxy, and that I'll have to remove it before I try to weld patches over the holes in the other parts of the frame.

The goal here is just to repair these pieces in-place, without pulling the body off and without access to a proper sandblasting system, a giant oven, or a way to submerge the frame.

Thanks!

-- Joe

All this work depends on how fussy you want to be and how much time you are willing to invest. For most people you would remove what is loose, POR-15 it and then topcoat it to color match. For the more anal among us you might try to sandblast it and then reapply epoxy of the correct color. For the truly ambitious they would cut out a section to gain access and clean it all up, epoxy paint it and then weld it back and reapply more epoxy. To paint inside you use a glove, a stick, and a rag. Put the rag into the paint and then stuff it into the hole and move it around as best as you can to distribute the paint as evenly as possible. There are large round rubber caps that cover those 2 holes. You might find them inside. As for the front damage, probably from leaking brake fluid. Grind or scrape it off and repaint. Heat and chemicals can cause too much collateral damage and is more toxic. You cannot weld if there is any trace of epoxy, it will contaminate the weld so it all has to be removed. Any rust too.

[jangell]

Thanks Dave. I wasn't sure if a grinder would be too aggressive and might damage the metal, but I guess I'll just have to be careful. Those are all from the engine cradle, BTW, not form the front of the car, so I don't know what caused it to crack.

I mostly want the frame to last another ten years at a minimum. I'd prefer not to cut the frame apart though, so I'll try slopping as much paint inside as I can to protect it.

Thanks!

-- Jot

[jangell]

I tried this yesterday and it worked great -- the angle grinder with a grinding wheel and very light pressure did a good job of removing the epoxy. It's pretty easy to tell when you're through due to the sparks flying when the wheel hits the steel beneath. The metal has an interesting mottled pattern on it now from the wheel, but it's not damaged. I went over it with a sanding disc to remove some of the smaller bits I missed with the wheel.

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The brown in the metal isn't rust, but simply reflections of the wood I used to level out the broken garage floor; the metal is nice and shiny. I'll probably have to remove some more epoxy around the holes I need to patch, I expect.

I'm off to read up on properly prepping for painting with POR-15, instead of just slopping some on like I've done before when I was in a hurry. Thanks!

-- Joe