On Not Getting Metal Fume Fever With Galvanized Conduit


You can find galvanized steel pipes at Home Depots and construction sites all around the world. These relatively thin-walled steel pipes would make for great structural members if it weren’t for the fact they were covered in a protective layer of zinc. This layer of galvanization lends itself to crappy welds and some terrible fumes, but badass, TV personality, and hacker extraordinaire [Hackett] shows us how to strip the galvanization off these pipes with chemicals available at any hardware store.

Since the galvanization on these pipes covers the inside and the outside, grinding the small layer of zinc off these pipes is difficult at best. To be sure he gets all the zinc off this pipe, [Hackett] decided to chemically strip the pipes with a cup full of muriatic acid.

The process is simple enough – fill a cup with acid, dunk the ends of the pipes, and clean everything up with baking soda. A great way to turn scrap pipe into a usable material, make a cool paper mache volcano, and avoid ‘ol galvie flu


46 thoughts on “On Not Getting Metal Fume Fever With Galvanized Conduit

  1. FYI. Most conduit is painted on the inside to make it easier to pull cable. Acid will not remove it and it will protect the zinc underneath. When you weld, that paint is gonna burn and fume some nasty stuff and then the exposed zinc is gonna fume off. Also, if it’s really, really old, it’s probably gonna be lead based. Either way, you should still use a good evacuation system. That or strip the paint first then acid etch.

    Note that the amount of zinc on the inside will be small compared to the outside due to the way zinc preferentially plates on the conduit.

    1. Most conduit as in ‘none I’ve ever seen from any of a dozen hardware stores’. Where are you finding this conduit painted inside with lead based paint that sparked your nanny warning?

      1. My point was that if it was very, very old. I used to work at a plant that made conduit from 1/2″ up to 4″. We also made IMC. All conduit was painted on the inside.

        If the conduit you’re salvaging was made from before the 70s (entirely possible, depending on where you get it from), it would have been made back when lead based paints were very common.

        This isn’t a nanny warning. It’s based on industry experience and knowledge of paint manufacturing.

  2. Hmm…. I’ve never noticed a meth lab. aisle at hardware stores I’ve been to. May be I should ask for help, “Excuse me, can you direct me to the meth lab. section, please?”


  3. I’ve used white vinegar to take the zinc of nuts and bolts before just have to let it soak for a couple hours.

    A harbor freight weed burner also works really well if you like fire.

  4. I’ve used this technique when I needed some “blued” allen-head bolts. I had a project where I needed some dark-colored bolt heads as I didn’t want the chrome-colored heads to show. The bluing agent, however, does not work on zinc. Since the only allen-head bolts I could find in the required size were zinc-coated, I used muriatic acid to remove the zinc. After rinsing the muriatic acid off, I used the bluing agent. The result looked like it was manufactured that way.

  5. 1) Alternatively, zinc dissolves in sodium hydroxide solution (lye/caustic soda). It won’t attack the steel conduit so can be left to soak. It would also strip any paint!
    2) Why call it muriatic acid? – it’s hydrochloric acid. Old names like that, brown oil of vitriol, sugar of lead and plumbago belong back with the alchemists.

    Sweating a coherer with argentum stannous eutectic.

    1. Fred, if you’re buying it at a hardware store you can pretty much count on the label saying “Muriatic Acid”. Not IUPAC compliant but if you need help finding it, it helps to call it what the guy at the store calls it.

      Asking a biochemist where they keep the 2-Aminopropanoic acid, while good for lulz is similarly unproductive.

      1. In my store they don’t sell muriatic acid, I even had to look it up through Wikipedia, to see what it actually is. This might be because I’m not from an English speaking country, and in schools we kind of skip over non IUPAC names in English class….
        And the IUPAC name for Alanine _is_ Alanine, by the way.

  6. A simple way to prevent fume fever is to drink milk. The chemicals in milk neutralize the zinc in the blood. I take your point in that prevention is better than cure, and you do get a better weld without the zinc. With stick welding you can always ramp up the amps,but you do run the risk of burn through. A good method to remove the coating I shall remember this for future jobs.

      1. It’s “arguable”, no real studies have been done. According to Wikipedia, an ocean of informed and balanced facts filtered thru a bunch of headcases with Asperger’s Syndrome.

  7. I’m all for saving $, but seems the conduit + the acid would cost more than just buying the proper materials for the job in the first place. or Why not just make weld free joints, like those frames for tarps are joined together with.

    1. EMT is *much* lighter. … That’s ElectroMechanical Tubing – the trade name for that kind of electrician-style pipe in my part of the world (Canada).

      If you *need* black iron pipe, by all means have at ‘er. But for a lot of things, EMT is just the thing. Sometimes it’s much better welded than setscrewed together with hardware store couplings. Plus, . . . welding practice!

    2. Because I ain’t made of money, and I get conduit for free or really cheap from the scrap yard. (Though many places will let you help yourself to what is in their scrap dumpster if you ask!)

      And black iron is great…if you are plumbing in natural gas or something… but a bit heavy for the stuff I build.

  8. Welding without arm and hand protection is dangerous too – skin cancers take a long time to develop, but once they start showing up, the damage is well and truly done. Cover up, your grandchildren will thank you.

  9. OK, let’s say I did a joint the same way Hackett did (I meant a metal joint, jeez people), what options would you use to make that joint last as long as the galvanized conduit? ‘Cause rust is already eating through that bare steel as we’re talking.

  10. @randykc galvanized paint.

    also to the person who called bull on milk, it’s true. Milk is what you would be told to drink if you called the poison control center. it’s also taught in welding trade school that if you have to weld galvanized you should drink milk at the end of the day if you feel as though you were over exposed to it.

    Source: me journeyman welder. Google it if you don’t believe me.

  11. You guys are completely missing the point of this and obviously know nothing of the genius that is chris hackett.chris hackett gets ALL of his materials from dumpster diving and the like. This is for a situation in which obtaining the materials you want isnt always possible. He did it out of necessity not because he didn’t want to go buy the stuff (which he wouldn’t have done anyway)
    I would highly suggest watching his show “stuck with hackett” it will give you a much better understanding as to why he did this.
    on a side note its good to know he hasn’t blown his head off doing his insane but amazing projects yet

  12. I dunno. That seems like too much work for the welding area involved. You only need maybe 1/8″ on the end of each pipe to be zinc free to make a decent weld with something as thin as EMT. It’d be faster to just use an angle-grinder with a wire wheel to remove the zinc.

  13. Yeah chromium poisoning.I suppose this saves wearing a hot sweaty mask under your helmet.

    Dont breath fumes from that acid bath highly corosive it will strip your face and your snozzles. I just hope buying the meratic acid in that quantity wont flag you as meth cooker or something else suspicious.

  14. You can buy muriatic acid by the truck load and no one will ask. I get in (4) 1 gallon cases. All you need to justify it is a swimming pool. It’s used to offset the alkalinity of the chlorine.

  15. I like it. I’ve wanted to build a lite but strong drive-through gate and thought conduit might be the answer, except for those pesky fumes when welded. This will do the trick nicely. Thanks the tip. p.s. very nice presentation.

  16. Re. avoiding the fumes…..don’t put a fan in front of you or behind you, put a fan to either side blowing away from you laterally. If you’re using MIG the fan will blow away your shielding gas and welds will be awful (if they even are welds). If you have to weld outdoors, use stick or flux-core wire feed. Also, cleaning the zinc off the outside of tubing doesn’t remove it from the inside. That muriatic acid process will take it off both inside and outside.

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