TIG welding primarily uses argon as the shielding gas.
Argon protects the weld area from contamination, prevents oxidation, and ensures a clean, strong weld.
CO₂ is not typically used in TIG welding, as it can cause spatter and weaken the weld.

Is TIG welding CO2 or argon?

TIG welding (GTAW – Gas Tungsten Arc Welding) uses inert gases, most commonly argon, not CO₂. Let’s go into detail about why and how the shielding gas works.

1. Purpose of Shielding Gas in TIG Welding

In TIG welding, the shielding gas is critical because:

Protects the molten weld pool from atmospheric contamination
- Oxygen, nitrogen, and hydrogen in the air react with molten metal → porosity, oxidation, brittle welds.
Protects the tungsten electrode
- The tungsten electrode is non-consumable but can oxidize if exposed to air, contaminating the weld.
Stabilizes the arc
- Argon allows a smooth, concentrated arc for precise control.

Without shielding gas, TIG welding is essentially impossible for quality work.

2. Why Argon is Used in TIG Welding

Argon is an inert noble gas, meaning it does not react with metals.
Properties making argon ideal:
1. Non-reactive → prevents oxidation and contamination.
2. Denser than air → forms a protective blanket over the weld pool.
3. Arc stability → concentrates heat and produces a smooth weld bead.
4. Versatile → suitable for steel, stainless steel, aluminum, copper, titanium.
Argon is the default gas for most TIG welding applications.

3. Why CO₂ Is Not Used in TIG Welding

CO₂ is not inert; it is reactive.
In MIG welding, CO₂ can be used because the electrode is consumable, and some oxidation can be tolerated.
In TIG welding:
- CO₂ reacts with the molten metal → porosity, oxidation, brittle welds.
- The non-consumable tungsten electrode can be damaged by CO₂.
- Arc becomes unstable → poor heat control and weld appearance.

Using CO₂ in TIG welding is almost never done because it produces inferior, contaminated welds.

4. Other Gas Options in TIG Welding

Helium: Sometimes mixed with argon for aluminum, copper, or high-thermal conductivity metals.
- Pros: hotter arc, deeper penetration.
- Cons: more expensive, arc can be less stable.
Argon/Helium Mixtures: Used for specialty metals to combine shielding and higher heat input.

5. Summary Table: Shielding Gases in TIG Welding

Gas	Used in TIG?	Purpose / Notes
Argon	✅ Yes	Standard, stable arc, inert, protects molten pool & tungsten
Helium	✅ Optional	Increases arc heat, deeper penetration for copper/aluminum
CO₂	❌ No	Reactive, oxidizes metal, damages electrode, unstable arc
Nitrogen	❌ No	Reactive, can form nitrides, only used in specialty processes

Conclusion:

TIG welding uses argon (or argon-based mixtures), not CO₂.
Argon protects the weld pool, stabilizes the arc, and prevents oxidation.
CO₂ is reactive and would ruin TIG welds, unlike MIG welding where CO₂ can sometimes be used.
For aluminum, helium or argon/helium mixtures are sometimes added for deeper penetration.