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I have an outdoor free standing light in my subdivision yard.

It is on a 5" diameter metal pole. This pole was driven into the ground and has rusted at the ground level and broken.

I need to fix it and want to prevent this from happening again. I prefer not to go to concrete since there are electrical wires in the ground.

How do I prevent this from rusting out again?

  • Good answers below... just to add that animal urine seems to accelerate rusting. Clean and paint regularly if this could apply. – Aloysius Defenestrate May 3 '15 at 20:46
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  1. Make sure concrete is above ground. 3-4" is usually good. This will keep standing water out.

  2. Paint metal before putting it in concrete. A metal primer and a sealant coat goes a long way.

  3. Slope concrete form away from pole on the top 1-2 inches. If you do this right the concrete at pole will be about a 1/2" taller than concrete at edges. Your pole is rusting quicker because of standing water.

  4. Caulk concrete to post gap.

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Make new post out of galvinzed pipe

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  • Galvanizing is a cost effective solution that would inhibit rust for many years. also, make it difficult for water to get inside the post and pool. – Hightower May 4 '15 at 5:26
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There are many options.

  • Stainless-steel pipe would be the simplest and most direct one, given your non-concrete desire.
  • For that matter, at 4-5" schedule 80 PVC conduit will probably work fine and never rust (it paints nicely) for somewhat less cost than stainless steel, unless this is a really tall light (seems unlikely, but you didn't say.) You'll probably have to go to a real electrical supply, not a home improvement store to find that. I guess you'd need to adapt for your light fixture, as 4" size is 4.5" OD, and 5" size is 5.563" OD. The ID on 5" is 5.04" so a section of the original 5" pole might slip inside it to hold the fixture at the top.
  • Concrete is not so hard to do with wires - just put the wires in PVC conduit, at least for the part in the concrete. Using a concrete base with mounting bolts embedded and a metal post with "feet" that go on the mounting bolts (held on by a nut below and a nut above) is the standard method of mounting metal light poles. The anchor bolts are tied into the reenforcing steel before the concrete is poured.
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Your problem has been solved by science! Use a galvanic anode. Attach a block of zinc (bare metal to bare metal) torward the bottom of your pole before you bury it. The one catch is that you may have to isolate the safety ground from the pole.

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I think it is pretty funny people think concrete prevents rust. What causes rust is water. Guess what is inside concrete? Water. Ever seen old bridges falling apart on the highway, with the rusty rebar sticking out and all brown and the concrete cracking and falling away. You know why that is? It is because concrete has water in it, and it rusts the rebar. They put that green crap on the rebar because they think it will stop the water, but it doesn't. My college recently rebuilt an entire 70,000 person stadium at a cost of $50 million because the old one was falling apart. Why? Because all the rebar was rusted. The Roman colisseum has lasted for 2000 freaking years. You know why? Because it has no freaking rebar in it. My college is going to rebuild that goddamn stadium every 50 years for the next 2000 years. I wonder how times they are going to rebuild it before they stop putting freaking rebar in it. Maybe they will never figure it out. They will just rebuild the stadium 40 times, over and over again at $50 million a pop. After they rebuild it 40 times it will cost $2 billion in modern day dollars.

Anyway, sorry for the rant. The way to stop metal from rusting is to keep it dry. This is why I have a dehumidifier in my basement where all my tools are. If I were you, I would dig a 12 inch hole, 24 inches deep and I would put 4 inches of gravel in it. If the location was flat or at a low point I would then bury drainage pipe 20" deep connected to the hole and leading to the nearest drain. Then I would put the light post in the hole and wire it up. Then I would fill in the hole with gravel. It will still rust, but should last about 40 to 50 years assuming it is neglected. If it is painted regularly it will last about 300 years until it rusts inside out. If it is painted regularly inside and out it will last forever.

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