You already know how to TIG weld, strike an arc, drop filler, lay a bead. So why do some welds come out clean and consistent while others go grey and porous the moment the part heats up? And why does aluminum feel like a different sport?
The welders who level up aren't the ones who memorize an amperage chart; they're the ones who can look at a bad weld and know what to change. Here are the TIG welding techniques that separate someone who can TIG weld from someone who lays consistently clean welds.
1. Start With a Clean TIG Setup
Most bad welds are bad setups revealing themselves three inches in. Proper TIG welder setup runs a chain: material → tungsten → filler → shielding gas → torch angle → torch speed.
Start with clean base metal and filler. Remove oil, grease, moisture, oxides, and other surface contamination before welding. Seat the right tungsten at the right stickout. Wipe your filler, because a dirty rod feeds contamination straight into the weld; buy quality rod like mild steel TIG rod or stainless TIG rod and store it clean. Then confirm argon, correct flow, and intact lines.
Before you strike an arc, think about torch angle and travel speed, too. Your torch angle directs heat into the joint while helping the shielding gas fully cover the molten puddle. Lean too far and you can direct heat away from the root while exposing the puddle to atmospheric contamination. Travel speed matters just as much: move too fast and you can end up with a colder weld and insufficient penetration; move too slowly and you dump excess heat into one area.
Run this chain every time and half the problems below never appear.
2. Master Heat Control, Not Just an Amperage Chart
The biggest thing that separates intermediate from advanced TIG: amperage isn't a fixed setting, it's a dial you work constantly.
A beginner sets 120 amps and welds at 120 amps. But the part doesn't stay the same temperature, heat builds as you travel, so that perfect 120 now floods a hot part and the puddle widens, sags, or drops out. Aluminum is especially unforgiving here: its high thermal conductivity and low melting point leave little margin for error, and it gives almost no colour warning before the puddle overheats and collapses.
When heat input changes throughout the weld, variable amperage control gives you more control over the puddle. A foot pedal works well at the bench, while a compatible torch-mounted remote can be useful out of position. Both let you taper amperage as the workpiece heats up.
Running too hot: the puddle grows faster than you can travel, the bead sags, or aluminum goes dull and falls in. Too cold: you won’t get enough penetration, filler balls up instead of flowing, and the bead sits tall and ropey. As the part heats, ease off the pedal and travel slightly faster to hold the same puddle. The goal isn’t a number, it’s a consistent puddle size from start to finish. Watch the puddle, not the meter.
3. TIG Contamination: Why Your Weld Looks Dirty
This is the most common thing welders troubleshoot, and it's worst on aluminum: black specks, grey sooty beads, welds that start clean and deteriorate. Work this list top to bottom:
- Base prep. Aluminum oxide melts at roughly 2,000°C, while the aluminum beneath it melts around 660°C. That high-melting oxide layer needs to be properly removed and managed before and during welding. Degrease first, then remove oxide.
- Your cleaning process. Start by wiping the aluminum with acetone to remove oil, grease, and other surface contaminants. Once the surface is clean, use a clean stainless steel brush dedicated exclusively to aluminum to remove the oxide layer. The order matters: brushing first can work oils and contaminants into the surface instead of removing them. Never use a brush that’s been used on other metals, as it can introduce cross-contamination. Keep an aluminum-only stainless steel brush in your kit.
- Filler. Wipe every rod.
- Tungsten. If the tungsten touches the puddle or filler and becomes contaminated, stop and regrind it before continuing. Welding with contaminated tungsten can compromise arc stability and weld quality.
- Torch angle and gas. Excessive torch angle can reduce shielding-gas coverage and expose the puddle to the atmosphere. Keep the torch relatively close to vertical, roughly a 10–15° travel angle is a useful starting point, and check gas coverage if a properly cleaned weld is still showing contamination.
If a TIG weld is contaminated or sooty, check material prep, tungsten and filler condition, and shielding-gas coverage before chasing machine settings.
4. Get Your Shielding Gas Right
“Use argon” is where most advice stops, but coverage is a system: flow rate + cup size + gas lens + torch angle + post-flow.
More flow isn’t better; too much creates turbulence that can pull surrounding air into the shielding zone. Around 15–20 CFH suits many jobs; set it with a proper gas regulator and quality argon. A gas lens diffuses and straightens the argon flow, providing more uniform shielding and allowing greater tungsten stickout when access requires it.
Cup size should match the material and application. A larger TIG cup paired with a gas lens can provide broader shielding coverage on stainless, while aluminum often benefits from a smaller cup and more focused gas coverage. This helps keep the AC arc and cleaning action concentrated rather than allowing the arc to wander. TIG gas lens collet bodies and cups make it easy to tailor the setup to the job.
Keep the torch close to vertical with roughly a 10–15° travel angle, pushing the torch in the direction of travel. As a starting point, allow roughly one second of post-flow per 10 amps of weld current to help protect the hot tungsten and weld as they cool. Adjust as needed for your machine and application.
5. Choosing the Right Tungsten, and Preparing It
Tungsten choice and condition show up constantly in TIG welding troubleshooting, and the rules changed. The old pairing was pure tungsten balled for AC and thoriated for DC. On many modern inverter TIG machines, 2% lanthanated (blue) and certain rare-earth tungsten electrodes are versatile options for both AC and DC welding and can be run with a prepared, tapered tip. Browse tungsten electrodes and keep a couple of diameters on hand.
Match tungsten diameter to your amperage range. An electrode that’s oversized for very low current can make arc starting and stability more difficult, while an undersized electrode can overheat, deform, or contaminate the weld. Grind lengthwise, so marks run down toward the tip; grinding across leaves ridges that make the arc wander. A taper of about 2–2.5× the diameter is a solid default: sharper for a focused low-amp arc on thin work, blunter for more current. Regrind the moment the tip blobs, discolours, or you dip it.
6. Dial In Your Machine
Set prep and consumables first, or the settings just send you chasing your tail. The point is understanding what each control does.
AC balance (aluminum) splits each cycle between electrode-negative (penetration, heat into the work, cooler tungsten) and electrode-positive (oxide cleaning, but hotter tungsten and less penetration). More cleaning means a hotter tungsten that needs to be bigger; more EN means deeper penetration. Around 70–75% EN is a useful starting point on clean aluminum, but follow your machine manufacturer’s recommendations and adjust based on what the weld shows. If you’re not getting enough oxide cleaning, increase EP; if you’re seeing excessive tungsten heating or etching, increase EN.
AC frequency changes the character and focus of the arc. Higher frequencies produce a narrower, more focused arc that can improve directional control and precision, while lower frequencies produce a broader arc. Around 100–150 Hz is a useful starting range on many modern inverter TIG machines, but adjust based on joint geometry, material, and the arc characteristics you want.
Pulse TIG welding alternates between peak current and lower background current, which can reduce average heat input depending on your settings. It’s a problem-solver, not a substitute for good puddle control. Reach for it to control heat on thin material, weld near edges, manage distortion, or lock in a steady rhythm. It helps a controlled welder; it won't rescue poor puddle control.
120V vs 240V. For Canadian home shops, available input power can affect how much welding output and duty-cycle headroom your machine provides. Dual-voltage TIG welders typically deliver their highest output when connected to the manufacturer’s specified 240V circuit, which becomes increasingly useful as material thickness and amperage demand rise. Rather than assuming a universal thickness limit for 120V, check your welder’s rated output and duty cycle at each input voltage. If aluminum is a priority, choose an AC/DC TIG machine with adequate output for the material and joint you’re welding.
7. Small Technique Changes That Make a Big Difference
- Keep a tight, consistent arc. Hold the tungsten close enough for a focused, controlled arc without touching the puddle, and maintain that distance as you travel. Consistent arc length is one of the keys to a stable, predictable puddle.
- Keep your torch angle close to vertical. A slight push angle, around 10–15° as a starting point, helps maintain shielding coverage while still letting you see the puddle.
- Filler rhythm, feed the leading edge of the puddle with an even dab-dab cadence, and keep the hot rod inside the gas envelope between dabs.
- Body position, brace and support your hands; you can't lay a steady bead from an unsteady hand. Good TIG welding gloves that let you feel the rod help more than people admit.
8. Practice With a Purpose
Endless beads plateau fast. Deliberate drills level you up quicker: hold a fixed arc length with no filler; add filler in a metronome rhythm; practice clean starts, stops, and restarts; run outside corners; and drop to thin sheet to learn where you blow through. Fifteen focused minutes beats an hour of aimless welding.
9. TIG Welding Troubleshooting Cheat Sheet
Start with the most common cause and work down. Always cross-check settings against your machine's documentation before changing them.
| Symptom | Likely cause | Fix |
|---|---|---|
| Grey, sooty aluminum weld | Surface contamination, inadequate shielding, contaminated tungsten/filler, or incorrect AC balance | Degrease and remove oxide; use an aluminum-only brush; check tungsten, filler and gas coverage; verify AC balance |
| Black specks in the puddle | Dirty filler/base; dipped tungsten | Wipe filler; re-clean base; regrind |
| Clean start, dirty mid-bead | Tungsten contamination, loss of shielding, or contaminated filler/base material | Regrind contaminated tungsten; check gas coverage and torch angle; verify filler and base metal are clean |
| Tungsten balls / spits | Excessive current for the tungsten size, too much EP, or unsuitable tungsten/setup | Check tungsten type and diameter against your machine’s recommendations; reduce EP or increase tungsten size if appropriate |
| Arc wanders | Radial grind; contaminated tip | Grind lengthwise; regrind |
| Puddle sags as you travel | Too much heat; no tapering | Back off pedal; travel faster; try pulse |
| Can't penetrate aluminum | Insufficient amperage, excessive EP, material thickness, or joint design | Verify amperage and AC balance; check machine output against the application; review joint preparation and technique |
Where to Go From Here
Leveling up your TIG isn't about buying gear until the welds fix themselves, it's clean prep, reading the puddle, protecting the weld, and knowing what each control does. Aluminum deserves its own deep dive on AC balance, frequency, and heat runaway, a companion guide worth reading next.
If you're upgrading as you go, we stock everything here, AC/DC TIG welders, torches, tungsten, gas lenses and cups, aluminum and steel filler rod, and gloves, shipped across Canada.
FAQ
Why does my aluminum TIG weld look dirty?
Dirty or peppery aluminum TIG welds can result from surface contamination, inadequate shielding gas, contaminated tungsten or filler, incorrect polarity, or insufficient AC cleaning action. Start by properly cleaning the aluminum and filler, checking the tungsten, and verifying gas coverage before fine-tuning AC balance.
Can you TIG weld aluminum on a 120V machine?
Yes, some 120V AC/DC TIG welders can weld aluminum, but their available output and duty cycle may be lower than when operating on 240V. The practical material thickness depends on the specific welder, joint, and application, so check the manufacturer’s output and duty-cycle ratings rather than relying on a universal thickness limit.
What tungsten should I use?
For many modern inverter TIG machines, 2% lanthanated tungsten is a versatile choice for both AC and DC welding. The best tungsten type and diameter depend on your machine, amperage, and application, so check the manufacturer’s recommendations. Grind the tungsten lengthwise and choose a diameter appropriate for your current range.