Can You TIG Weld with 75% Argon and 25% CO2? 

No, you should not TIG weld with 75% Argon and 25% CO₂ because the CO₂ creates oxidation, spatter, and unstable arc conditions that compromise weld quality. Using 100% argon is recommended for TIG welding most materials.   

Below, we go into more detail on why you should not TIG weld with 75% Argon/25% CO₂ and alternatives for various TIG welding applications. 

Why CO₂ Is Problematic in TIG Welding

Carbon dioxide is fundamentally incompatible with TIG welding because it’s an active gas that reacts with molten metal, while TIG welding requires completely inert shielding to maintain arc stability and prevent chemical reactions at the weld pool. 

Unlike MIG welding, where some reactivity can be beneficial, TIG welding requires complete atmospheric protection around the non-consumable tungsten electrode and molten metal.

Carbon dioxide disrupts this environment through its reactive nature. This reactivity causes:

• Oxidation of the weld pool, leading to porosity and weak joints
• Carbon introduction into the weld, altering mechanical properties
• Erratic arc behavior that makes precise control difficult
• Increased spatter that contaminates the work surface
• Tungsten electrode contamination requiring frequent regrinding

Even in a 75/25 mixture where argon provides most of the shielding, the 25% CO₂ component is enough to destabilize the entire welding process.

What Are the Material-Specific Impacts of Using CO₂ in TIG Welding?

The 75/25 argon/CO₂ mixture is unsuitable for all materials that are commonly TIG welded, with severity ranging from complete failure on aluminum and stainless steel to poor quality results on mild steel.

Aluminum

CO₂ causes severe oxidation and porosity in aluminum welds. The reactive gas breaks down the protective oxide layer that forms naturally on aluminum, leading to visible discoloration and contamination, structural weakness from porosity, and poor penetration and bead appearance.

Stainless Steel

The carbon from CO₂ can form carbides in stainless steel. Using 75/25 argon/CO₂ results in reduced corrosion resistance, potential for stress corrosion cracking, and poor weld aesthetics and finish quality.

Mild Steel

CO₂ is commonly used for MIG welding mild steel. But TIG welding with 75/25 argon/CO₂ produces excessive sparking and spatter, poor arc control and stability, and severely compromised weld quality despite being the most CO₂-tolerant material.

Titanium and Specialty Alloys

These materials require absolutely pristine inert gas coverage. Any CO₂ contamination causes immediate and severe oxidation.

What Should You Use Instead for TIG Welding?

Pure argon is recommended for TIG welding most materials, argon-helium mixtures provide enhanced heat input for thick sections, and specialized mixtures serve specific material requirements.

Tyler O'Brien

Tyler is a results-driven marketing professional specializing in the industrial gases and equipment industry, bringing his 10 years of technical expertise and digital marketing acumen to the complex industrial gas B2B environment.