What Is TIG Welding?
TIG stands for Tungsten Inert Gas welding. Its formal process name is GTAW, or Gas Tungsten Arc Welding. Unlike MIG welding, where the wire electrode continuously melts into the joint, TIG uses a non-consumable tungsten electrode to create the arc. The welder controls the weld pool directly and adds filler metal separately when required. That control is why TIG welding aluminum is widely used for thin material, appearance-sensitive work, repair work, and quality-critical joints.
Table of Contents
How TIG Welding Works
The Arc, Tungsten Electrode, Shielding Gas and Weld Pool
These four elements work together:
| Element | Main role | What happens when it is poorly controlled |
|---|---|---|
| Arc | Provides concentrated heat | Unstable heat input, poor fusion, erratic puddle |
| Tungsten electrode | Carries and stabilizes the arc | Arc wandering, contamination, difficult starts |
| Shielding gas | Protects tungsten and molten aluminum from air | Blackened welds, porosity, oxidized tungsten |
| Weld pool | The molten metal that becomes the weld bead | Collapse, lack of fusion, excessive reinforcement or burn-through |
For most beginner aluminum TIG applications, use high-purity argon and keep the gas flow steady. The exact flow depends on cup size, gas lens, torch angle, tungsten stick-out, ambient drafts, and joint geometry—not simply one fixed number.
Aluminum is sensitive to heat input and surface contamination. TIG helps because it provides a stable arc, controllable heat input, and clean bead formation when the workpiece is properly prepared. For beginners, the greatest benefit is visibility: TIG allows you to watch the oxide layer break down, wait for a shiny puddle, and add filler only after the molten aluminum is properly wetted. Miller’s guidance similarly recommends waiting until a clean, shiny puddle forms before adding filler, because adding wire before oxide removal can contaminate the weld.
How to TIG Weld Aluminum Alloys
Aluminum TIG welding begins with understanding the surface, not with selecting an amperage. Aluminum conducts heat quickly and forms a dense oxide film almost immediately in air. While the base metal melts at a relatively low temperature, the oxide film remains intact much longer and can prevent the weld pool from wetting and joining properly. This is why aluminum welding is not simply a matter of increasing current. The first priority is to remove the oxide film effectively, then control heat input, gas shielding, and the highly fluid weld pool.
Understanding Aluminum Alloy Properties
Aluminum has a relatively low melting temperature compared with steel, but it also conducts heat much faster. This creates a familiar beginner experience:
- The workpiece initially seems slow to form a puddle because heat is escaping into the surrounding material.
- Once the material heats up, the puddle can suddenly widen and lose support.
- Thin material can then collapse or burn through if current, travel speed, or filler addition is not adjusted.
Aluminum also does not change color as clearly as steel when approaching melting temperature. Instead of relying on color, watch the surface: a properly cleaned puddle becomes bright, shiny, and fluid.
Characteristics of Aluminum Oxide Film
Aluminum naturally forms a thin, dense oxide film when exposed to air. This film reforms quickly after cleaning and has a much higher melting temperature than the aluminum beneath it. In practice, that means the base metal can begin to melt while the oxide layer still resists wetting and fusion. The result may look like a dull or sluggish puddle that refuses to flow together.
Why Aluminum Oxide Affects TIG Welding
If oxide remains on the surface or in the joint area, it can:
- Prevent the weld pool from wetting into the joint edges.
- Increase the risk of lack of fusion.
- Make the arc less predictable.
- Contribute to contamination and poor bead appearance.
- Trap surface contaminants that increase porosity risk.
The EP portion of the AC cycle provides the cleaning action that helps remove surface oxides; the EN portion provides stronger workpiece heating and penetration. AC balance lets the operator adjust that EN/EP relationship.
How to Remove Aluminum Oxide Before TIG Welding Mechanical Cleaning
AC cleaning action is useful, but it is not a substitute for preparation. Before welding:
- Remove oil, grease, fingerprints, and cutting fluid using an approved solvent and a clean lint-free cloth.
- Let the surface dry completely.
- Remove oxide using a clean stainless-steel wire brush reserved only for aluminum, or another approved mechanical cleaning method.
- Keep filler rod clean and dry.
- Avoid touching the prepared joint with bare hands.
Never use a steel-contaminated brush on aluminum. Cross-contamination can introduce particles that interfere with weld quality.
AC TIG Cleaning Action
During AC TIG welding, the EP portion of the cycle helps break up aluminum oxide through cathodic cleaning. The EN portion directs more heat into the workpiece, improving penetration and reducing tungsten heat loading. Use the machine’s AC balance control to supply adequate cleaning—not excessive cleaning. A very wide etched zone may look dramatic, but it can indicate too much EP time, increased tungsten balling, and reduced effective penetration. Fine-tune balance according to oxide thickness and surface condition.
What Are The Key AC TIG Welding Parameters for Aluminum?
Aluminum TIG welding settings vary with material thickness, alloy, joint design, welding position, and torch setup. Instead of relying on one fixed parameter set, use the table below to understand each control, establish a practical starting point, and adjust it based on arc and weld-pool behavior.
Always verify final settings on test pieces before production welding.
Aluminum AC TIG Welding Settings: Functions and Adjustment Guide
| Parameter | Start Here | Main Effect | Too Low | Too High |
|---|---|---|---|---|
| Welding Current | Approx. 40–50 A per mm of material thickness | Heat input and penetration | Slow puddle; poor fusion | Wide puddle; burn-through |
| AC Frequency | 80–120 Hz | Arc width and focus | Wider, softer arc | Narrower, less forgiving arc |
| AC Balance | 20–30% cleaning action (EP) | Oxide cleaning vs. penetration | Oxide remains; poor wetting | Wide etch; tungsten balling |
| AC Waveform | Square wave | Arc feel and heat distribution | Less control for the joint | Overly reactive puddle |
| Shielding Gas | Use high-purity argon | Protects arc and weld pool | Oxidation; porosity | Turbulence; air entrainment |
| Tungsten Stick-Out | Keep as short as practical | Gas coverage and arc stability | Poor access or visibility | Weak shielding; unstable arc |
Welding Current for Aluminum TIG Welding
Welding current is the main driver of heat input. It controls how quickly the puddle forms, how wide it becomes, and how deeply the joint fuses.
- Too little current: The arc may sit on the surface without establishing a fluid puddle. This can lead to poor sidewall fusion and insufficient penetration.
- Too much current: The puddle grows too wide, the edges lose definition, and thin aluminum can collapse or burn through.
Do not treat amperage as an isolated setting. A current that works at one travel speed may overheat the joint when the welder slows down. If the puddle begins to sag, first consider reducing heat input, increasing travel speed, adding filler strategically, or using a more suitable joint setup.
AC Frequency for Aluminum TIG Welding
AC frequency is the number of polarity changes per second. It affects the width and stiffness of the arc cone.
- Lower AC frequency: Produces a broader, softer arc and a wider, flatter puddle. This can be useful when a wider heat spread is desired.
- Higher AC frequency: Produces a narrower, more focused arc with stronger directional control. It is often useful for fillets, corners, and narrower joints.
AC Balance for Aluminum TIG Welding
AC balance determines the time or current distribution between EN and EP portions of the AC cycle. The exact display language varies by machine: some machines show EN percentage, some EP percentage, and some use “cleaning” or “balance” terminology. Always check the equipment manual before interpreting a percentage.
- More EP/cleaning helps remove oxide but increases tungsten heating and can widen the etched zone.
- More EN/penetration directs more heat into the workpiece and improves penetration, but may leave insufficient cleaning on heavily oxidized material.
A practical rule: start with a clean surface and use the least cleaning action that still gives a bright puddle and stable wetting. If the puddle looks dull, contaminated, or slow to open, clean the material first; then adjust balance only as needed.
AC Waveforms for Aluminum TIG Welding
Modern AC/DC TIG machines may offer several waveform options. Names and characteristics vary by manufacturer, so treat the following as a general guide rather than a universal rule.
| Waveform | Typical arc behavior | Typical application tendency |
|---|---|---|
| Advanced square wave | Fast polarity transition, focused arc | Directional control and productive welding |
| Sine wave | Smooth, traditional AC arc characteristic | General-purpose or traditional AC feel |
| Triangular wave | Reduced average heat input in some implementations | Heat-sensitive or thinner material applications |
Waveform selection should support the weld pool you need—not be treated as a cosmetic setting. If you are learning, begin with the machine’s recommended default waveform, stabilize your current, frequency, balance, and torch technique first, then compare waveforms on test coupons.
Common Aluminum TIG Welding Problems and Solutions
Most aluminum TIG problems can be traced to one of four causes: poor preparation, inadequate shielding, unsuitable heat input, or inconsistent torch control.
| Problem | Likely causes | First checks and corrections |
|---|---|---|
| Difficulty starting the arc | Dirty or poorly prepared tungsten, poor work clamp contact, incorrect start settings | Clean/regrind tungsten, check grounding, confirm start mode and gas pre-flow |
| Unstable TIG arc | Contaminated tungsten, excessive arc length, gas leak, incorrect gas flow | Regrind tungsten, shorten arc, inspect hose and fittings, stabilize shielding |
| Black or contaminated aluminum welds | Inadequate shielding, contaminated material, excessive tungsten stick-out, drafts | Clean material, check argon flow and nozzle, reduce stick-out, block drafts |
| Porosity in aluminum TIG welds | Moisture, oil, dirty filler rod, gas shielding loss | Degrease and dry material, clean filler, inspect for gas leaks and turbulence |
| Lack of fusion | Current too low, travel too fast, oxide not removed, poor fit-up | Improve preparation, adjust heat input/travel speed, verify joint fit-up |
| Insufficient weld penetration | Low effective heat input, excessive travel speed, unsuitable joint design | Increase effective heat input, slow slightly, review joint preparation |
| Burn-through | Excessive heat input, slow travel, large joint gap, thin material overheating | Reduce heat, increase travel speed, control gap, consider pulse or backing |
| Poor weld-bead formation | Unsteady torch angle, variable arc length, irregular filler timing | Maintain consistent arc length, torch angle, travel speed, and dab rhythm |
AC Balance for Aluminum TIG Welding
AC balance determines the time or current distribution between EN and EP portions of the AC cycle. The exact display language varies by machine: some machines show EN percentage, some EP percentage, and some use “cleaning” or “balance” terminology. Always check the equipment manual before interpreting a percentage.
- More EP/cleaning helps remove oxide but increases tungsten heating and can widen the etched zone.
- More EN/penetration directs more heat into the workpiece and improves penetration, but may leave insufficient cleaning on heavily oxidized material.
A practical rule: start with a clean surface and use the least cleaning action that still gives a bright puddle and stable wetting. If the puddle looks dull, contaminated, or slow to open, clean the material first; then adjust balance only as needed.
AC Waveforms for Aluminum TIG Welding
Modern AC/DC TIG machines may offer several waveform options. Names and characteristics vary by manufacturer, so treat the following as a general guide rather than a universal rule.
A Simple Troubleshooting Order
When the weld does not look right, do not immediately change every parameter. Follow this order:
- Check cleanliness: base metal, filler rod, tungsten, and joint edges.
- Check gas protection: gas supply, fittings, flow, nozzle condition, and drafts.
- Check tungsten: correct preparation, no contamination, suitable stick-out.
- Check heat input: current, travel speed, arc length, and puddle size.
- Check AC settings: balance, frequency, and waveform after the basics are confirmed.
In Conclusion
Successful aluminum TIG welding starts with oxide removal, then depends on controlled heat input, stable shielding gas, and consistent torch technique. For reliable results, choose an AC/DC TIG welder with adjustable current, AC frequency, and AC balance. The JASIC EVO20 TIG AC/DC series provides the control needed for stable arc performance, effective oxide cleaning, and consistent weld-pool control.