TIG Welding Aluminum Settings: Amperage Chart, AC Balance & Filler Selection

TIG welding aluminum requires AC polarity, 100% argon shielding gas at 15-25 CFH, and a pure or ceriated tungsten electrode. Set your AC balance to 65-70% EN, AC frequency to 80-120 Hz, and amperage to roughly 1 amp per thousandth of inch of material thickness.

Aluminum’s high thermal conductivity and low melting point (1,220°F compared to 2,500°F for steel) make heat management the central challenge. The metal goes from solid to liquid with almost no color change, and it conducts heat away from the weld zone three times faster than steel. You’ll need more amperage than you’d expect, a foot pedal for real-time heat control, and clean material to get consistent results.

Amperage Settings by Thickness

The “1 amp per thou” rule gets you in the ballpark, but real-world settings depend on joint type, position, and how much heat sink the part creates. Thicker base material and T-joints pull more heat away, pushing you toward the high end of the range.

These ranges assume flat position butt joints on prepped material. Vertical and overhead positions use the lower end of the range. Lap joints and outside corners run cooler because heat dissipates into both pieces. T-joints and inside corners trap heat and may need less amperage than you’d expect for the thickness.

AC Balance Control

AC balance controls the ratio between electrode negative (EN) and electrode positive (EP) portions of the AC cycle. This is the single most misunderstood setting on a TIG welder for aluminum work.

EN (electrode negative) puts heat into the workpiece. This is the penetration half of the cycle. More EN means deeper penetration and a narrower bead profile.

EP (electrode positive) provides the cleaning action. During EP, the arc blasts oxide off the aluminum surface. Without EP, the oxide layer (melting point 3,700°F) prevents the aluminum underneath from fusing. More EP means a wider cleaning zone and a wider, shallower puddle.

Recommended AC Balance Settings

• 65-70% EN for general fabrication on clean, prepped aluminum. This is the sweet spot for most work.
• 75-80% EN for thick material where you need maximum penetration and the aluminum is freshly cleaned.
• 55-60% EN for dirty, oxidized, or cast aluminum that needs aggressive oxide removal.

Running too much EP (below 50% EN) balls the tungsten tip and overheats the electrode. Running too much EN (above 80%) may not clean the oxide sufficiently, causing porosity and poor fusion.

AC Frequency

AC frequency determines how many times per second the arc transitions between EN and EP. Higher frequency narrows the arc cone and gives you more directional control. Lower frequency spreads the arc wider.

• 60-80 Hz for wider beads and more cleaning action on thicker aluminum or fillet welds.
• 80-120 Hz for general-purpose welding. This range works for most joints.
• 120-200 Hz for tight joints, thin material, and detailed work where you need a focused arc.
• 200+ Hz for very thin material and precision work. The arc becomes very tight and responsive.

Start at 100 Hz for general work and adjust based on how the puddle behaves. If the puddle wanders too much, increase frequency. If you need to wet out wider, decrease frequency.

Filler Rod Selection: 4043 vs. 5356

These two filler alloys cover 90% of aluminum TIG work. Choosing the wrong one won’t always cause a weld failure, but it can hurt strength, corrosion resistance, or appearance.

ER4043

• Silicon-based alloy (5% Si)
• Flows smoothly into the puddle with minimal spatter
• Produces bright, shiny beads
• Lower melting point than 5356, so it wets out easier
• Best for: 6061, 6063, 3003, casting alloys, general fabrication
• Not recommended for: sustained high-temperature service above 150°F, parts that will be anodized (turns dark/blotchy)

ER5356

• Magnesium-based alloy (5% Mg)
• Stiffer rod, feeds less smoothly but creates stronger welds
• Duller, whiter bead appearance
• Higher shear strength than 4043
• Best for: 5052, 5083, 5086, structural applications, marine aluminum, anodized parts
• Not recommended for: use on aluminum castings (crack-sensitive with casting alloys)

Quick Selection Guide

Tungsten Selection for AC Aluminum

Pure tungsten (green band) was the traditional choice for AC aluminum because it forms a clean ball on the tip during AC welding. Modern inverter machines with adjustable AC balance and frequency have made other options viable.

2% ceriated (gray band) works well on inverter machines with high AC frequency. It maintains a sharper tip than pure tungsten and starts easier. This is a good all-around choice if you weld both steel and aluminum and don’t want to swap tungsten constantly.

2% lanthanated (blue band) performs similarly to ceriated on AC. Slightly better arc stability at low amperages.

Pure tungsten (green band) still works fine for transformer-based machines and lower AC frequencies. It balls up predictably and handles the EP portion of AC without splitting.

Grind the tungsten to a blunted point for AC work. Start with a 30-degree included angle taper, then blunt the tip slightly. The arc will form a small ball during welding. On inverter machines at higher frequencies, you can run a sharper point than on older transformer machines.

Shielding Gas

100% argon is the standard gas for TIG aluminum. Flow rates depend on cup size and working conditions.

• #6 cup (3/8"): 12-15 CFH
• #7 cup (7/16"): 15-18 CFH
• #8 cup (1/2"): 18-22 CFH
• #10 cup (5/8"): 20-25 CFH
• Gas lens setup: Add 3-5 CFH above standard cup flow rates. The improved gas coverage is worth the extra argon.

For thick aluminum (1/4" and up), a 75/25 argon/helium mix increases heat input without cranking amperage. Helium raises the arc voltage, which puts more energy into the workpiece. The tradeoff is higher gas cost and faster flow rates (helium is lighter and disperses quicker).

Drafts are the enemy of aluminum TIG. Even a light breeze strips the shielding gas away and causes instant porosity. Block drafts with welding curtains or cardboard barriers. If you’re welding outdoors, increase flow rate by 5-10 CFH and use a larger cup or gas lens setup.

Material Preparation

Aluminum oxide must be removed before welding. The oxide melts at 3,700°F while the aluminum underneath melts at 1,220°F. If you don’t remove it, the oxide floats on top of the puddle and creates inclusions.

1. Degrease the joint area with acetone or a dedicated aluminum cleaner. Don’t use brake cleaner or chlorinated solvents near an arc.
2. Remove oxide with a stainless steel wire brush dedicated to aluminum. Never use a brush that’s touched steel. Brush in one direction, not back and forth.
3. Fit-up tight. Aluminum’s high thermal conductivity means gaps cause burn-through on thin material and cold laps on thick material.
4. Weld within 2-4 hours of cleaning. Oxide reforms quickly, especially in humid conditions.

Filler rod also needs to be clean. Wipe rods with acetone before use. Don’t grab rods with greasy gloves.

Preheating Thick Aluminum

For aluminum thicker than 1/4", preheat helps overcome the material’s heat-sinking ability. Without preheat, you’ll struggle to establish a puddle and may burn through thin areas while the thick sections stay cold.

Preheat to 200-300°F. Use a temperature-indicating crayon or infrared thermometer to verify. Don’t exceed 350°F, especially on heat-treated alloys like 6061-T6. Excessive preheat can reduce the temper and weaken the base material.

On large parts, the section you’re welding cools as heat conducts away to the rest of the piece. Tack and weld in a pattern that manages heat buildup. Skip welding (welding a tack on one end, then the other, then the middle) distributes heat more evenly than welding straight through.

Technique Tips for Aluminum

Push the puddle. Point the torch in the direction of travel at a 15-20 degree angle. Pushing keeps the shielding gas ahead of the puddle and gives you a clear view of the leading edge.

Add filler to the leading edge. Dip the rod into the front of the puddle, not the center. If you dip into the center, the rod melts into a ball and doesn’t flow into the joint properly.

Use a foot pedal. Aluminum’s rapid heat buildup means you’ll start at high amperage to establish the puddle, then back off as the workpiece heats up. A foot pedal gives you real-time control. Without one, you’ll burn through the end of every bead. For more on amperage control options, see foot pedal vs. fingertip TIG controls.

Watch the puddle size. Keep it consistent. If the puddle grows, you’re putting in too much heat. Back off the pedal. If it shrinks, add heat. On thin aluminum, the puddle can go from perfect to blown through in under a second.

Post-flow matters. Set post-flow to 1 second per 10 amps of welding current, minimum 5 seconds. Aluminum stays reactive at elevated temperatures longer than steel. Insufficient post-flow causes the tungsten tip and the end of the weld to oxidize.

Common Problems and Fixes

Porosity

Small holes or clusters of holes in the weld are almost always caused by contamination or insufficient shielding gas. Check these in order:

1. Dirty base metal or filler rod
2. Draft blowing gas away
3. Gas flow too low (or too high, which causes turbulence)
4. Moisture in the argon line (purge the line for 10 seconds before striking an arc)
5. Condensation on cold aluminum (wipe and preheat)

Black Soot Around the Weld

Too much EP (cleaning action) or too low AC frequency. Increase EN balance to 70-75%. If you’re already there, increase AC frequency. Also check that you haven’t contaminated the tungsten by dipping it into the puddle.

Cracking

Aluminum cracking usually comes from wrong filler selection or too much restraint in the joint. High-silicon 4043 is more crack-resistant than 5356 on 6061 base metal. If parts are heavily fixtured, allow for thermal expansion or use a more crack-resistant filler like 4047.

Tungsten Contamination

If the tungsten dips into the puddle, aluminum alloys onto the tip. This contaminates every weld until you regrind. Break off the contaminated tip, regrind to a point, and restart. Keep a spare pre-ground tungsten nearby so you don’t lose momentum.

Burn-Through on Thin Material

Drop amperage, use pulse, or increase travel speed. On material under 0.060", pulse settings of 1 PPS (pulse per second) at 30-40% background current give the puddle time to solidify between pulses. Also check that your fit-up is tight with no gaps.

Pulse TIG for Aluminum

Pulse TIG alternates between a high peak current and a low background current at a set frequency. On aluminum, pulsing helps control heat input on thin sections and produces a distinctive “stacked dimes” appearance.

Key pulse settings for aluminum:

• Peak amperage: Set to what you’d normally weld at without pulse
• Background amperage: 20-40% of peak
• Pulses per second (PPS): 1-3 PPS for visible ripple pattern, 30-100+ PPS for arc stability without visible ripple
• Peak time: 40-60% of the cycle

Start with 1 PPS, 50% peak time, and 30% background. This gives a clear, rhythmic cadence where you dip filler during each peak pulse. The background current keeps the arc lit without adding significant heat.

For a deeper look at how tungsten choice affects your AC arc on aluminum, see the tungsten electrode guide. For cup and gas lens options that improve gas coverage, check the TIG cup size guide.