Quick answer: GTAW stands for gas tungsten arc welding. It’s the same process most people call TIG welding (tungsten inert gas). An electric arc forms between a non-consumable tungsten electrode and the metal, while argon gas shields the weld from the air. You add filler rod by hand, separately from the arc. GTAW makes the cleanest, most precise welds of any common process, and it’s the go-to for stainless steel, aluminium, thin metal and pipe.
GTAW is slower and harder to learn than MIG or stick, but it gives you control the others can’t match. This guide covers how it works, the gear you need, the settings that matter, and how to start laying good beads.
What does GTAW stand for?
| Term | Means | Notes |
|---|---|---|
| GTAW | Gas Tungsten Arc Welding | The official name used by the American Welding Society (AWS) and in welding codes |
| TIG | Tungsten Inert Gas | The everyday name; same process |
| Heliarc | An old trade name | From the 1940s, when helium was the shielding gas |
| 141 | ISO 4063 process number | The European code for TIG with solid filler wire |
So “GTAW welding”, “TIG welding” and “GTA welding” all describe the same thing.
How GTAW works
These steps happen in order every time you weld:
- The arc starts. The machine starts an arc between the tungsten and the work, either with a high-frequency spark that jumps the gap or by touching and lifting the tungsten (“lift-arc”).
- Argon flows through the torch cup and covers the tungsten, the arc and the molten puddle, keeping oxygen and nitrogen out.
- The arc melts the base metal into a small, controllable puddle. The tungsten itself doesn’t melt; it’s non-consumable.
- You dab filler rod into the front edge of the puddle with your other hand, if the joint needs filler. Thin edge and corner joints can be fused without any.
- You control heat with a foot pedal or a fingertip control, so you can raise amps as the part heats up and taper off at the end.
- Post-flow gas keeps shielding the hot tungsten and weld for a few seconds after the arc stops, so neither oxidises.
Because heat and filler are controlled separately, you can weld very thin metal, make tiny precise welds, and produce welds with almost no spatter.
GTAW equipment
- Power source: a constant-current (CC) welder. DC-only machines weld steel, stainless steel, copper and titanium. AC/DC machines also weld aluminium and magnesium. Look for high-frequency (HF) start for the cleanest starts; lift-arc works but takes practice.
- TIG torch: air-cooled torches are fine up to roughly 150–200 A. Water-cooled torches are smaller and cooler for long jobs at higher amps.
- Tungsten electrode: see the tungsten section below.
- Cups (nozzles) and a gas lens: a gas lens smooths the gas flow so you can stick the tungsten out further and still get good coverage.
- Shielding gas, regulator and flowmeter: usually 100% argon.
- Filler rods: matched to the base metal.
- Foot pedal or finger control for amperage.
- Ground clamp, helmet, thin TIG gloves and a stainless wire brush kept only for TIG.
Shopping for a machine? See our guide to the best TIG welders for beginners.
GTAW shielding gas
| Gas | Use | Notes |
|---|---|---|
| 100% argon | Almost everything: steel, stainless, aluminium, chromoly, titanium | The default; buy this first |
| Argon–helium (e.g. 75/25) | Thick aluminium and copper | Hotter arc and deeper penetration; costs more and needs higher flow |
| Argon + small % hydrogen | Some austenitic stainless work | Specialist; never use on carbon steel or aluminium |
- Flow rate: about 15–25 CFH (7–12 L/min) for most work. More isn’t better, because too much flow causes turbulence that pulls air in.
- Never use CO₂ or MIG mix (argon/CO₂) for TIG. The oxygen in CO₂ attacks the tungsten and contaminates the weld.
- Back-purge stainless steel and titanium pipe or tube with argon on the inside of the joint, or the root will oxidise (“sugar”) and lose its corrosion resistance.
- Shield the area from wind. Even a fan can blow away your gas coverage.
Tungsten electrodes: types and colours
Tungsten types are identified by a colour band on the end (AWS A5.12):
| Type | AWS class | Colour | Best for |
|---|---|---|---|
| 2% lanthanated | EWLa-2 | Blue | All-rounder for AC and DC; a popular modern choice |
| 1.5% lanthanated | EWLa-1.5 | Gold | AC and DC; behaves much like thoriated |
| 2% ceriated | EWCe-2 | Grey (older stock: orange) | Low-amp DC work, thin metal, small parts |
| 2% thoriated | EWTh-2 | Red | DC on steel and stainless; long the standard |
| Zirconiated | EWZr-1 | Brown | AC aluminium on transformer machines |
| Pure tungsten | EWP | Green | AC aluminium on older transformer machines |
Thoriated tungsten is slightly radioactive. Grinding creates dust you shouldn’t breathe, so use local extraction, or switch to lanthanated, which most welders now do.
Tungsten size by amperage (DC electrode negative, typical)
| Diameter | Typical range |
|---|---|
| 0.040” (1.0 mm) | 15–80 A |
| 1/16” (1.6 mm) | 70–150 A |
| 3/32” (2.4 mm) | 150–250 A |
| 1/8” (3.2 mm) | 250–400 A |
Grinding tips: grind lengthwise (grinding marks pointing toward the tip), never around the circumference. That keeps the arc stable. For DC, grind a point about 2–2.5 times as long as the tungsten diameter. For AC on inverter machines, a point with a small flat tip works well.
Polarity and settings
- DCEN (DC electrode negative) is used for steel, stainless, chromoly, copper and titanium. About two-thirds of the heat goes into the work, so the tungsten stays cool and sharp.
- AC is used for aluminium and magnesium. The positive half of the cycle breaks up the tough oxide layer (“cleaning action”), and the negative half does the melting. On inverter machines you can adjust the AC balance (more cleaning or more penetration) and frequency (a higher frequency gives a tighter, more focused arc).
Amperage rule of thumb: about 1 amp per 0.001” of thickness (about 40 A per mm) for steel. Use a little less for stainless, which holds heat, and a little more for aluminium, which spreads it.
Starting settings: mild and stainless steel (DCEN)
| Thickness | Amps | Tungsten | Filler rod | Argon |
|---|---|---|---|---|
| 1/16” (1.6 mm) | 50–70 A | 1/16” | 1/16” ER70S-2 or 308L | 15 CFH |
| 1/8” (3.2 mm) | 90–125 A | 3/32” | 3/32” | 15–20 CFH |
| 3/16” (4.8 mm) | 130–170 A | 3/32” | 3/32”–1/8” | 20 CFH |
| 1/4” (6.4 mm) | 160–200 A | 1/8” | 1/8” | 20–25 CFH |
Starting settings: aluminium (AC)
| Thickness | Amps | Tungsten | Filler rod | Argon |
|---|---|---|---|---|
| 1/16” (1.6 mm) | 60–90 A | 1/16” | 1/16” 4043 or 5356 | 15–20 CFH |
| 1/8” (3.2 mm) | 120–150 A | 3/32” | 3/32” | 20 CFH |
| 3/16” (4.8 mm) | 170–200 A | 1/8” | 1/8” | 20–25 CFH |
These are starting points. Fine-tune by watching the puddle, and check your machine’s chart. For stainless use 308L filler on 304, and 316L on 316.
How to TIG weld: technique
- Clean everything. TIG is unforgiving: remove mill scale, oil, paint and oxide. Wipe with acetone. For aluminium, use a dedicated stainless brush right before welding.
- Fit up tight and tack every few inches.
- Hold the torch at about 10–15° from vertical, tipped in the direction of travel. Keep the arc short, about the diameter of the tungsten.
- Form a puddle before adding filler. Wait for a shiny, round pool.
- Dab the filler into the leading edge of the puddle, then pull it back slightly. Keep the hot end inside the gas shield, but never let it touch the tungsten.
- Move forward steadily, keeping the puddle the same size. Small steps of dab, move, dab give the classic “stacked dimes” look.
- Taper off with the pedal at the end so the crater doesn’t crack, and keep the torch over the weld during post-flow.
If you touch the tungsten to the puddle, stop. A contaminated tungsten won’t hold a clean arc. Break off or grind away the contaminated end and regrind.
GTAW pipe welding
TIG is the standard for the root pass on pipe in power plants, refineries, food and pharmaceutical plants, and for stainless or chromoly tube, because it gives a full-penetration, clean root that can pass X-ray inspection.
- Positions: the hardest common test is 6G, with the pipe fixed at a 45° angle so you weld in every position.
- Walking the cup is a technique where you rock the ceramic cup along the joint for steady travel. It’s common on heavy-wall carbon and stainless pipe.
- Purging: stainless and chromoly roots must be back-purged with argon.
- Typical procedure: a GTAW root and hot pass, then GTAW or stick (SMAW) fill and cap passes, depending on the procedure.
GTAW on aluminium
Aluminium is where TIG really shines, but it’s also where most beginners struggle.
- Use AC, 100% argon, and 4043 filler (general use, flows well) or 5356 (stronger, better colour match after anodising).
- Aluminium doesn’t change colour before it melts, so watch for the surface to turn shiny and wet.
- It conducts heat away fast. Start with more amps, then back off on the pedal as the part heats up.
- Clean it right before you weld. Its oxide layer re-forms within hours.
Advantages and disadvantages of GTAW
| Advantages | Disadvantages |
|---|---|
| Highest-quality, cleanest welds, with no spatter or slag | Slowest common process |
| Welds the widest range of metals, including aluminium, stainless, titanium and copper | Hardest to learn, because it needs both hands (and often a foot) |
| Excellent on thin material | Needs very clean metal and calm air (poor outdoors in wind) |
| Precise heat control | Equipment and gas cost more than stick |
| Welds without filler when it’s not needed | Lower deposition, so it’s uneconomical on thick plate |
GTAW vs MIG vs stick
| GTAW (TIG) | GMAW (MIG) | SMAW (Stick) | |
|---|---|---|---|
| Electrode | Non-consumable tungsten | Consumable wire | Consumable flux-coated rod |
| Shielding | Argon | Argon/CO₂ mix | Flux |
| Speed | Slow | Fast | Medium |
| Learning curve | Steep | Easiest | Medium |
| Thin metal | Excellent | Good | Poor |
| Outdoors / wind | Poor | Poor (good with flux-core) | Excellent |
| Best for | Precision, stainless, aluminium, pipe roots | Production and fabrication | Repairs, structural, field work |
For a wider overview, see types of welding processes.
Common GTAW problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Tungsten turns black or blue, arc wanders | Contaminated tungsten, low post-flow, wrong gas | Regrind the tungsten, increase post-flow, use pure argon |
| Porosity (holes) | Dirty metal, draughts, leaks, too much or too little gas | Clean better, block wind, check hoses, set 15–25 CFH |
| Grey, “sugary” back of stainless | No back-purge | Purge the inside with argon |
| Crack in the crater at the end | Arc stopped too quickly | Taper amps down with the pedal; add filler as you finish |
| Undercut along the edges | Too much heat or a long arc | Lower amps, shorten the arc, add filler at the edges |
| Black soot on aluminium | Oxide layer or not enough cleaning action | Clean right before welding; increase the AC balance toward cleaning |
Safety
- The UV is intense. Use an auto-darkening helmet set to around shade 10–13 depending on amperage (check your helmet’s chart), and cover all skin. TIG burns like a bad sunburn.
- Ventilate. The arc makes ozone, and some metals (galvanised steel, stainless) release harmful fumes.
- Grind thoriated tungsten only with extraction, or switch to lanthanated.
- HF start can interfere with pacemakers and nearby electronics. Check with your doctor if you have an implant.
- Wear proper welding clothes: flame-resistant cotton or leather, never synthetics.
GTAW welding certification
Certification shows you can make sound welds to a specific code and procedure. Common ones:
- AWS D1.1 (structural steel) is the standard US structural code, often tested in the 3G and 4G plate positions.
- ASME Section IX covers pressure vessels and piping in power, process and petrochemical plants. GTAW pipe tests are typically done in 6G.
- API 1104 covers pipelines.
- AWS Certified Welder testing is done at AWS-accredited test facilities, which many community colleges and trade schools run.
Most welders learn through a trade school or community college programme, then certify to the specific procedure their employer uses. Certifications usually need to be kept current by welding regularly with that process.
FAQ
Is GTAW the same as TIG?
Yes. GTAW (gas tungsten arc welding) is the formal name; TIG (tungsten inert gas) is the common one. They’re the same process.
What gas is used for GTAW?
Almost always 100% argon. Argon–helium blends are used for thick aluminium and copper. Never use CO₂ or MIG gas mixes.
Can you TIG weld without filler rod?
Yes. “Autogenous” welding fuses the edges together without filler, which works well on thin outside corners, edge joints and tight-fitting thin sheet.
Do you need to preheat for GTAW?
It depends on the metal, not the process. Thick carbon steel, high-carbon and alloy steels such as chromoly in heavy sections, and cast iron often need preheat to prevent cracking. Follow the welding procedure or filler maker’s guidance. Thin mild steel and stainless usually don’t need it.
Can GTAW weld aluminium?
Yes, with an AC-capable machine. It’s one of TIG’s biggest strengths.
Is TIG welding hard to learn?
It’s the hardest of the common processes, because it uses both hands and usually a foot pedal at once. Most people lay decent beads on steel within a few weekends of practice. Aluminium and out-of-position pipe take much longer.
Can I run a TIG welder on a generator?
Yes. Size the generator to the welder’s input with our welder generator size calculator, and choose a generator with clean power (low THD) for inverter TIG machines.
How this guide was researched: tungsten classifications follow AWS A5.12. Settings ranges come from manufacturer and training charts and are starting points only. Always follow your machine’s guidance and any welding procedure you work to. See how I test and review.