Aluminium is one of the most rewarding materials to weld, but it can also be one of the most frustrating if your TIG welder isn’t set up correctly.

Unlike steel and stainless steel, aluminium requires AC (Alternating Current) TIG welding to break through the tough oxide layer that naturally forms on the surface. Using the correct machine settings, tungsten electrode, shielding gas and preparation techniques is essential for producing clean, strong welds.

This guide explains everything you need to know to correctly set up your TIG welder for aluminium welding.

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Why Aluminium Requires AC TIG Welding

Aluminium develops a layer of aluminium oxide immediately when exposed to air.

This oxide layer:

• Melts at approximately 2,000°C
• Aluminium itself melts at approximately 660°C
• Prevents proper fusion if not removed

AC TIG welding alternates between:

Electrode Negative (EN)

Provides:

• Penetration
• Heat into the workpiece
• Faster travel speeds

Electrode Positive (EP)

Provides:

• Oxide cleaning action
• Surface preparation during welding
• Better weld appearance

The balance between these two cycles creates the ideal conditions for aluminium welding.

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Equipment Required

For AC TIG welding aluminium you will need:

✓ AC/DC TIG welder

✓ 100% Argon shielding gas

✓ TIG torch with gas lens

✓ Suitable tungsten electrode

✓ Dedicated stainless steel wire brush

✓ Aluminium filler wire

✓ Clean, contaminant-free material

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Choosing The Correct Tungsten

Modern inverter TIG welders perform best with:

Gold (1.5% Lanthanated)

Excellent all-round choice.

Suitable for:

• AC aluminium welding
• DC steel and stainless welding

Advantages:

• Excellent arc starts
• Long life
• Stable arc

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Purple (E3 Rare Earth)

Popular modern alternative.

Advantages:

• Excellent arc stability
• Good current carrying capacity
• Suitable for AC and DC welding

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White (Zirconiated)

Traditional aluminium tungsten.

Advantages:

• Excellent resistance to contamination
• Maintains balled tip well

Often preferred for transformer-based TIG welders.

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Tungsten Size Guide

Tungsten SizeTypical Current Range1.0mmUp to 70A1.6mm40-150A2.4mm100-250A3.2mm200-350A

For most aluminium fabrication work:

2.4mm tungsten is the most versatile choice.

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Shielding Gas Selection

For most aluminium TIG welding:

100% Argon

Suitable for:

• Thin aluminium
• General fabrication
• Most workshop applications

Gas Flow Rate:

10-12 L/min with a gas lens.

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Argon / Helium Mixes

Used for:

• Thick aluminium
• High production welding

Advantages:

• Increased penetration
• Faster travel speeds

More commonly found in industrial applications.

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AC Balance Settings

AC Balance controls the ratio between cleaning action and penetration.

Starting Point

70% EN / 30% EP

or

30% Cleaning

This setting works well on most modern inverter TIG welders.

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More Cleaning Required

Increase EP if:

• Material is heavily oxidised
• Weld appears dirty
• Black contamination forms around the weld

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More Penetration Required

Increase EN if:

• Material is clean
• More penetration is required
• Tungsten overheating occurs

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AC Frequency Settings

AC Frequency controls arc focus.

Lower Frequency (50-80Hz)

Produces:

• Wider arc
• Wider weld bead
• Better for thicker material

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Higher Frequency (100-200Hz)

Produces:

• Narrower arc
• Better directional control
• Improved corner welding

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Recommended Starting Point

100Hz

Suitable for most aluminium welding applications.

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Amperage Settings

A useful guideline:

Approximately 40 Amps Per Millimetre

Examples:Material ThicknessStarting Amperage1mm40-50A2mm80-100A3mm120-150A4mm160-200A6mm240A+

Always adjust based on joint design and travel speed.

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Pulse Settings (Optional)

Pulse is not essential but can improve control.

Typical starting settings:

• Pulse Frequency: 1-2Hz
• Peak Current: 100%
• Background Current: 30-40%

Benefits:

• Reduced heat input
• Better puddle control
• Improved appearance

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Aluminium Filler Wire Selection

4043 Aluminium Filler

Most commonly used.

Suitable for:

• General fabrication
• Cast aluminium
• Easier welding

Produces smooth flowing welds.

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5356 Aluminium Filler

Suitable for:

• Structural applications
• Marine environments
• Higher strength requirements

Provides greater tensile strength.

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Material Preparation

Preparation is critical.

Before welding:

✓ Remove grease and oil

✓ Clean using acetone

✓ Use a dedicated stainless steel brush

✓ Remove all oxide contamination

✓ Store filler wire clean and dry

Poor preparation causes more aluminium welding problems than machine settings.

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Common Aluminium TIG Welding Problems

Black Soot Around The Weld

Possible causes:

• Insufficient gas coverage
• Contaminated material
• Excessive torch angle
• Incorrect AC balance

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Tungsten Contamination

Possible causes:

• Touching the weld pool
• Excessive EP setting
• Incorrect tungsten size

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Poor Penetration

Possible causes:

• Amperage too low
• Travel speed too fast
• Excessive cleaning balance

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Dirty Weld Appearance

Possible causes:

• Inadequate cleaning
• Surface contamination
• Incorrect gas coverage

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Recommended Starting Setup

For welding 3mm aluminium:

• AC Mode
• 140A
• 2.4mm Gold or Purple Tungsten
• 100% Argon
• 10-12 L/min Gas Flow
• AC Balance: 70% EN
• AC Frequency: 100Hz
• 4043 Filler Wire

This setup provides an excellent starting point on most modern AC/DC TIG welders.

Key Takeaway

Successful aluminium TIG welding relies on four things:

Clean material, correct tungsten, proper AC balance and adequate shielding gas.

Get these fundamentals right and achieving clean, strong aluminium welds becomes significantly easier regardless of the machine you use.