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This railing on our deck is exposed to the elements (in Chicago, so rain and snow), and has corroded through. The railing is hollow, and it seems to be completely full of water. It's swollen near the corrosion site, and I assume it'll get worse quickly now that it's in this condition.

I'd like to drain out the water and seal the top, but I can't imagine successfully wicking all the water out, and don't know how to go about perforating the bottom, for it to drain completely. How might an experienced DIY-er deal with this problem?

the hole, direct view from above, showing nearby corrosion side view, showing swelling

Edit: Thank you all so much for the awesome responses - I'm going to talk through the options with my spouse and we'll figure out which to try!

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    You could drain it by drilling, then heating, then tape the crack and shoot it full of expanding hydrophobic foam. Trim foam protrusion from holes/crack, sand smooth, repaint. Dec 23 '20 at 0:00
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    In the 2nd picture, it very much looks like the vertical post has rusted through, too. If that's the case, then that entire section of railing is suspect and likely needs to be repaired/replaced. I'm not sure what floor you're on, but you don't want to fix up the horizontal rail just to have a friend lean on it at a party and tumble over the edge when the post gives way.
    – FreeMan
    Dec 23 '20 at 0:59
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    @Freeman- I agree about the post being damaged (good eye! +1) and being wary of component failure.
    – ojait
    Dec 23 '20 at 1:10
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    @Freeman I'd have said that was rust staining from standing rusty water inside the (uncoated) internal of the horizontal bar leaking out through the weld and discoloring the vertical post..
    – Caius Jard
    Dec 23 '20 at 14:17
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    Entirely possible, @CaiusJard, however, I wanted to be sure to point the issue out to the OP to ensure he looks at it in his assessment of repair/replace, and to ensure that it's considered for repair if that's the direction he goes.
    – FreeMan
    Dec 23 '20 at 14:24
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That's pretty far gone, basically that split is beyond economical repair.

But since you asked:

To drain it, it can be drilled from below the deck using a long drill bit, or a slot can be cut using a hacksaw with the blade sideways or reversed, or you could remove rail unit from the house and just use a regular drill.

To dry it you can heat it with a propane torch or heat gun until it stops steaming.

You can then cover the split with duct tape, might be good for a year or two, a better repair of that split seems pointless

Basically to fix this properly you need to replace that bottom rail. That means removing the unit from the house, cutting out the old rail and welding a new one in. After that consider having the whole thing hot dip galvanized before re-coating it and fitting it back onto the house. The person doing the welding probably knows a place that can do the galvanizing.

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    +1 for gone beyond economic repair - time to replace that section of railing, and possibly the whole thing.
    – FreeMan
    Dec 23 '20 at 1:00
  • Powder coating it, after replacement, would also be an option that'll last for years without needing a new coat. The welder might also know a powder coater, too. Dec 23 '20 at 19:57
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The swollen steel at the split is from oxidation (rust). I agree with your plan to remove trapped water in the rail. The procedure calls for moderate DIY skills and some special tools.

I'd initially start by drill a 1/4 inch hole near the split. Start drilling on the top section of the rail continuing through to and out the bottom. It may be easier to keep the drill bit on target if you strike a dimple with a punch first.

If the rail is level water may still be trap any where in the rail. But to remove from the damaged area is a good first step. So with that in mind drill again to the left and right of the split same as before.

I agree with the other person suggestion regarding applying heat to expidite evaporation of trapped water. You'll probably blister some paint but that's easily repairable. Heat gun would be best (if you have one), but a hair dryer works ,too. Propane torch as a last resort. If water is trapped you will hear and see steam eminating from your drain holes. It should evaporate under the heat source fairly quick.

I'd recommend grinding the swollen area of the split, but it isn't critical. Next you need to plug the drain holes and split. What I suggest for this is a (2) part epoxy such as JB Weld, PC-7 or an epoxy dough.

The dough is best since it won't run through the holes. Knead the two parts together until uniform in color (gray) and push into opening. It can be smoothed with acetone and a rag, but wait for it to set and then sand with a 100 grit paper.

I'd leave the bottom drain holes open so that any remaining/future moisture will not be trapped.

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    +1 for leaving drain holes open at the bottom.
    – FreeMan
    Dec 23 '20 at 0:59
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    The post probably needs a drain hole (or had one that is plugged.) If water is collecting in this rail to the point that it's "full" the bottom of the post is surely also "full" and being stressed by freezing. The swollen steel at the split is actually a classic pattern of frozen pipes - part of the pipe freezes, blocking water from moving, then more freezes and the pressure rises, until finally the pipe bulges and gives way when the pressure is high enough in the part that's still liquid. So the fundamental problem here is blocked drains or lack of drains. Condensation will always get in.
    – Ecnerwal
    Dec 23 '20 at 1:52
  • TLDR - it's probably more frozen than rusted out. The raw steel where it broke open from freezing will rust, of course.
    – Ecnerwal
    Dec 23 '20 at 2:00
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    OP might put two holes in the pipe. and push hot air in one from the heat gun so it flows out the other hole which is down the other end. Or maybe the replacement length should be C channel not a tube or pipe. Or even solid bar, if the weights and cost allows.
    – Criggie
    Dec 23 '20 at 12:38
  • if you have a compressor blowing air in one end may help to clear the trapped water.
    – Jasen
    Dec 23 '20 at 20:06
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That is a failed / defective ERW weld seam . So corrosion did not cause the problem it exposed it , corrosion is not severe. Drill a few holes in the bottom to drain any water. Replacing that section of pipe is the best way to fix the hole. For an inexpensive repair ,you could caulk it and paint to match . First power wire brush and treat with conversion coating ( such as Navel Jelly ). PS ; much of my job was identifying bad ERW seams in Amoco pipelines.

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  • "navel jelly" - more persistent than fluff, I find ;)
    – Caius Jard
    Dec 23 '20 at 16:34
  • A bad weld that then corroded isn't going to buckle the tube. Chicago: this was from freezing, and although that section of seam might be poor, I'm sure it would've been fine w/o water getting in at the post and then freezing.
    – Mazura
    Dec 24 '20 at 2:36
  • Yes and no. That is not remotely enough deformation/ bulging to rupture sound steel . And there is a chance that residual stress opened it some after splitting. ERW is made from flat stock that is cold formed to a round then the weld edges are pushed together ( it is actually a forge weld). For ordinary pipe like this there is no further heat-treatment , so it has significant residual stress. Dec 25 '20 at 19:57
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Before you come up with a repair plan you need to know how bad it really is. I would hit it, and the questionable post too, with a hammer to see how badly it's rotted. It might be fairly solid or it might start crumbling. If it doesn't crumble or cave in you can patch it. Any areas that cave in should be replaced. If you patch it there's some good answers here and the only thing I would add is to find the low spots with a level and drill drain holes there.

If it needs to be replaced then I would cut that entire piece of square tubing out with an angle grinder using a cut off wheel. After that grind the post smooth and find someone to weld a new piece on.

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  • how bad it really is, +1, why it happened, and where (at the post), and how to keep it from happening again. Fixing the rail is phase two. Connection at the post is phase one.
    – Mazura
    Dec 24 '20 at 2:41

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