Copper is not hard to TIG weld, but it does some unique properties that you have to keep in mind. Copper is a very efficient conductor of heat, so the workpiece will heat up quickly when you start to weld. Be ready to handle the heat and wear adequate protective gear if you are going to weld copper. You also need to move fast once you start the weld because the heat that makes the weld puddle dissipates quickly in copper.
So, how to TIG weld copper? The steps to TIG welding copper are:
- Buy oxygen-free copper for TIG welding
- Get the other materials needed: electrodes, welding rod, shielding gas
- Gather equipment for welding
- Sharpen the electrode and set up collet
- Set up the welder for TIG welding copper
- Clean the copper
- Put away solvents
- Check ventilation—copper fumes are toxic
- Dress for welding
- Preheat the copper with a propane torch
- Crack a spark and make a puddle
- Move fast, so you don’t lose the puddle
- Let it cool slowly
TIG welding copper is not hard, but it doesn’t get done that often. It is different than steel, but it is straightforward enough. You can’t treat copper-like steel; the little details are various. Pay attention to those, and your project will be fine.
Step 1: Buy the Right Copper
If you are TIG welding copper, buy oxygen-free copper. Some grades of copper have oxygen dissolved in the metal. The oxygen will corrode your weld bead under the heat of TIG welding. Oxygen-free copper doesn’t have this problem, and it takes TIG welds beautifully.
Oxygen-free copper is the most commonly available grade of copper available today because it is the best grade for electrical applications. You can buy oxygen-free copper from most metal yards. There are different grades of oxygen-free copper with differing levels of purity. The ATSM designations for oxygen-free copper are:
- C11000 or electrolytic tough-pitch (ETP) copper for 99.9% pure copper
- C10200 or oxygen-free (OF) copper for 99.95% pure
- C10100 or oxygen-free electronic (OFE) copper is 99.99% pure
- There are designations for copper with high levels of purity, but those are for very specialized applications like cryogenics or extreme temperature exposure
C11000 is the least expensive grade of oxygen-free copper and is fine for any welding project. You only need the higher grades if an engineer specifics them in a welding plan.
Don’t buy second-hand copper from scrapyards for TIG welding. If the copper isn’t oxygen-free, the welds will bubble and crack. They can even corrode. Corroded welds will be weak and brittle. If you don’t use oxygen-free copper, your welds will be ugly at best. At worst, they won’t hold.
Watch for Zinc
Copper alloyed with zinc makes bronze. Some grades recycled of copper can include a little bit of zinc. When TIG welding, the zinc can evaporate due to the high heat and produce highly toxic fumes. If you are joining junkyard copper, braze or solder it instead of TIG welding.
Copper for Food (and Drink)
If you are welding copper for handling potable water (or stronger drinks), use pure copper-not alloys. Alloys can leach metals into the liquid that aren’t good for drinking. The leaching is worse at high temperatures, like boiling a liquid and containing the steam.
Some metals can even cause blindness if ingested. If you are building copper for food handling, don’t use scrap copper-only new. It is dangerous to construct food-handling equipment from unknown grades of metal.
Step 2: Gather Other Materials
In addition to the material being welded, TIG welding requires an electrode to carry the current, a separate rod that melts to form the weld, and shielding gas to protect the weld from corrosion under the heat of the arc.
Choosing an Electrode
Many different electrodes can be used to TIG weld copper. Some recommended electrodes include:
- 1.5% lanthanated tungsten (gold tip)
- 2% lanthanated tungsten (blue tip)
- Thoriated tungsten (red tip)
- Rare earth mix (purple tip)
- Ceriated tungsten (grey tip)
Any of these electrodes can successfully weld copper. Each has its characteristics in terms of ease of striking an arc, durability, and fitness for AC or DC settings. Choose one that you are familiar with, or experiment to see what works best for you.
Rods for Welding Copper
Unlike other kinds of welding, in TIG welding the rod is separate from the electrode. While you hold the electrode with one hand to make an arc, you need to feed the rod in with the other hand to get a weld puddle and draw out the weld.
For high-end jobs, deoxidized copper TIG rods are available. These rods are formulated for TIG welding copper and will provide a clean, attractive, and strong weld. Once the weld has cooled, the color of the weld will be almost exactly the same as the copper workpiece. These rods aren’t cheap, but they will give excellent results.
For stronger welds, choose silicon-bronze rods. These rods will give a strong and durable joint. Silicon-bronze rods are very common, and they are less expensive than pure copper rods. These rods are also suitable for joining different metals together, so reach for them if you need to join copper to steel or iron.
If appearance is a concern, you can also use 1/8 inch strips of parent metal as welding rods. Trim thin strips of waste material from the projecting copper and use them as welding rods. The final weld will be the same color as the base material. With a little grinding, the finished piece will look as though it wasn’t welded at all. This is also an excellent way to use up scraps of copper that aren’t worth recycling.
If you are just practicing your copper welds, you can use stripped Romex wire as a welding rod. It won’t be as strong or attractive as using commercial rods or the parent metal, but Romex is cheap and easy to find. Many shops have a coil, or two of Romex stashed somewhere that can be put to use.
Metals oxidize quickly under the extreme heat of TIG welding. To prevent this, TIG welders feed a steady stream of an inert shielding gas into the arc to protect the weld while it is so hot. There are a variety of gasses and gas mixes available for TIG welding.
For TIG welding copper, use pure helium or 80% helium / 20% argon for the shielding gas mix. Pure helium transmits 1.7 times more heat than pure argon. Copper requires lots of heat to weld, so getting the most out of your shielding gas is helpful. If you are welding thick material or your welder has limited amps, use pure helium.
You can weld copper using pure argon as a shielding gas, but it’s an uphill battle. If your piece is thin or you have a big welder, you probably make pure argon work. If you are using a small welder on thick copper, you may not be able to weld copper successfully in argon. If you can’t get enough heat for a good weld in pure argon, get some helium instead.
Step 3: Other Equipment Needed
All the equipment needed for welding copper is available in a well-stocked welding shop. Gather your equipment before you start working on the project. You will need:
- Bench grinder for preparing the electrode before you weld
- Wire brush for removing oxidation from the weld surface to the weld will hold. The best brushes for cleaning copper have fine-textured stainless steel bristles. Use a dedicated brush for copper; don’t try to clean with a brush that has all kinds of crud on it already.
- Acetone or another solvent to remove all traces of grease, paint, and other contaminants from the weld surface. Citrus degreaser is also a good choice for cleaning metal, and it’s not flammable
- Protective equipment to keep you safe and secure while you weld. You need a mask, gloves, long-sleeved shirt or leather jacket, and heavy jeans or welding chaps.
- Respirator mask to protect you from toxic copper fumes
- Propane torch to preheat the workpiece
Step 4: Sharpen the Electrode
Copper welds best with a pointed electrode. If your electrode does not have a sharp point, use a bench grinder to refresh the tip. New electrodes can be purchased with a sharp tip. Once the tip is ready, put the electrode into the collet and tighten it. Adjust the gas flow on the handpiece based on the manufacturer’s recommendations.
If you are doing lots of TIG welding, you can save time on sharpening electrodes with an electrode grinder. These work like a pencil sharpener (except for tungsten!) to quickly give you perfect points on your electrodes.
Step 5: Set Up the Welder
Copper is a heat sink and requires lots of heat to weld. Some pros use as much as 300 to 400 amps for thick pieces of copper. You need a big welder to put out the amps required for thick copper. Consult the manual for your particular welder for the best settings to TIG weld copper. Unless you are working with very thin sheets, you can crank the amps up without damaging the copper.
After the welder is set up, be sure to connect the return clamp from the welder to the workpiece or the worktable. You can’t get a spark if you don’t have a circuit.
Double-check the grounding for your welder as well. Copper is a great conductor of electricity, and any problem with the grounding can cause it to shock you. You should always check the grounding, but make a point to check if you are working with big pieces of copper. Make sure not to touch the copper with bare skin to avoid shocks.
Step 6: Clean the Copper
Clean the copper well. Remove paint and grease with a solvent such as acetone, methyl ethyl ketone, or lacquer thinner. If there is any patina or oxidation on the surface, scrub it off with a fine-bristle stainless steel brush. The weld won’t hold if you try to work with a dirty surface.
If the surface has never been painted, you don’t have to use a solvent. Using a citrus-based degreaser is effective in removing all traces of grease. Degreaser smells much better than solvents, and it’s not flammable. That’s a nice safety feature in a welding shop.
Step 7: Put Away Solvents
If you used a flammable solvent to clean the copper, put it away now. You don’t want to have volatile chemicals out when you are dealing with the high heat of welding. The copper you are welding is potentially hot enough to ignite solvents on its own. Make sure it doesn’t have the chance.
Step 8: Check Ventilation
Make sure you have excellent ventilation when TIG welding copper. Copper fumes produced by TIG welding are toxic. If you aren’t sure about the ventilation, you should wear a respirator while welding. Symptoms of inhaling copper take four to twelve hours to appear, so you likely won’t know you have a problem until you are finished welding. Put on the respirator, even if it’s uncomfortable.
Step 9: Dress for Welding
You always need a mask, gloves, and cover for your upper body when welding. You can wear a leather welding jacket or a long-sleeved, flame-retardant shirt to weld. For welding copper, you need a little extra protection as well.
Copper is the best conductor of heat that most people will ever weld. The heat from welding will quickly spread throughout the entire piece. If you are working with large pieces, make sure to have enough clothing on your legs as well as your arms to keep from being burned if you contact the copper away from the weld. Have plenty of cold drinking water on hand and take breaks before you overheat.
Step 10: Preheat the Copper
Because copper will absorb heat quickly and distribute the heat through the entire work piece, it can be hard to keep a weld puddle. To help the copper stay hot enough to weld, preheat the whole part to a temperature between 300 and 750 degrees. This is particularly important for sheet copper because the heat spreads in all directions. A pipe is a little easier to keep hot because the heat can’t spread as far.
To preheat your piece, use a propane torch over the whole surface of the project to bring the temperature up quickly. Copper is easy to heat, and hot spots aren’t a big problem. The heat will flow evenly through the piece as you use the torch.
Step 11: Weld the Joint
When you are ready to weld, put the pieces together, and secure them in place. To crack a spark, hold the tip of the electrode about an inch from the joint and press the pedal with your foot. Hold the arc at 70 degrees to the surface of the copper. Strike an ark and push in the rod to make a puddle.
Once you have a puddle, use the tip of the rod to spread the bead down the joint. Keep feeding the rod into the weld and spreading the pool with the rod. Once you have started the weld, copper is easy to work with. Keep the arc going and feed the rod at a steady rate.
If you are working with very thin sheets, be careful about warping. The immense heat from TIG welding can warp the material. If you are working with very thin or delicate pieces, brazing or soldering might be a better choice than TIG welding.
There is one caution for welding copper: don’t dawdle. Copper’s ability to absorb heat means the piece can cool more quickly than you think. The heat from the arc will dissipate rapidly in the copper. If you are too slow, you will lose the puddle and have to start a new arc and puddle.
Step 12: Cool Slowly
Cool copper welds slowly to prevent weld cracking. Preheating the entire piece helps with this as there is more heat to dissipate. Burying the part in the sand or covering it with a fiberglass blanket can also slow the cooling process. Give it plenty of time to cool before you do anything else with it.
Fabricating Copper Projects
The most common use for copper is the wiring, which doesn’t require welding. The other everyday use for copper is heat exchange piping in refrigerators, HVAC units, and industrial equipment; this piping is usually brazed or soldered instead of welded. Now that you know how to weld copper, what should you make?
Copper has become a popular material for decorative elements in architecture. Many kitchens now incorporate a copper backsplash or range hood, which can be welded. Using copper tubing to make furniture gives an attractive appearance that you can’t get with steel or aluminum. Copper has always been popular for external elements like weathervanes and cupolas.
If furniture and home décor doesn’t float your boat, remember one other widespread use for copper: making distilling equipment. TIG welding is a great way to put together a still, but check the laws before you do….just because you can weld up a moonshine still doesn’t mean you should.