Welding EMT Conduit

I use EMT (Electrical Metallic Tubing)  conduit in a lot of my projects. EMT is cheap, smaller sizes are bendable and it is readily available at local home supply stores.

There are potential health problems welding EMT however. Please read this (and other Instructables warnings) before you consider welding EMT.

The biggest problem is that toxic fume are given off when the welding arc heats up the galvanized coating on the EMT. These fumes (mostly zinc oxide) are toxic, as in poisonous to breathe!

See this Instructable for a description of the risk: http://www.instructables.com/id/Bicycle-cargo-trailer--200-lb-capacity%2c-%2430-for-pa/step11/Safety-considerations/

NOTE: DO ALL OF THESE STEPS OUTDOORS IN A WELL VENTILATED AREA!

I am an amateur welder (not even close to an expert!) and to minimize the risk as much as possible I use these three steps when welding EMT.

BE CAREFUL. BE EXTRA SAFE. DON'T BREATHE IN ANY FUMES EVER. DON'T GET IN A HURRY AND SKIP ANY SAFETY PRECAUTIONS. USE A RESPIRATOR IF YOU ARE NOT POSITIVE YOU ARE AVOIDING THE FUMES.

Step 1 Vaporize the Coating

1. Heat the EMT to vaporize as much of the galvanized coating as possible. I use a MAPP torch (I don't know if propane would work.) to thoroughly heat the area(s) where I will be welding. Do this outside. (Photo #1) The galvanized coating will vaporize and leave a brown residue (Photo #2 arrow)

Comments

[andersonhdj]

Most anythng galvanised can be welded using a stick welder and 316 stainless electrodes, there's no spatter or striking problems and an excellent weld is obtained. As usual, BEWARE OF THE FUMES!!

[valveman]

If using any acid to dissolve the galvanized coating, don't forget to wash the tubing well or the acid will keep working. Another option is to grind off the galvanized area you want to weld. As an extra precaution, buy a half face respirator like the 3M 3600 with 2097 filters. These fit well and can be used with practically any welding helmet.

[Phil B]

I am guessing you are using a MIG welder. Do you need to weld in short bursts to avoid blowing holes in the tubing, or are you able to run a continuous bead? I have used a stick welder on EMT. The heat was about as low as I could go without sticking the rod. Starting an arc was difficult, so I used a piece of carbon rod. See my previous Instructable on that. I used 1/16 inch 6013 rod and welded in short bursts. There was some grinding to be done afterward to make the welds look decent. For me, the difficult thing was to weld "T" joints like you have in your photo. The butted piece heats up faster at the end than the continuous piece does at the joint. It is very easy to blow holes.

[2 stroke]

i use a stick welder too 1/16 7018 works better though

[purplewg]

A method I use is dipping the ends to be welded in Muratic acid. Yeah, the same stuff they use in pools. It etches the galv right off.

[Hubiewan]

Thanks, I love this hint. I have some sort of acid around and it'll keep me from using up Mapp. Very cool.