Shielding gases create an inert atmosphere around the molten weld pool, displacing oxygen and nitrogen from the air that would otherwise cause porosity, oxidation, and embrittlement in the finished weld. The gas forms a protective blanket that prevents atmospheric contamination during the critical moments when the metal is molten and reactive.
How Shielding Gases Protect the Weld Pool
The Protection Mechanism
- Displacement of atmospheric gases. The shielding gas pushes away oxygen (21%) and nitrogen (78%) from the weld zone.
- Creating an inert environment. Noble gases like argon provide complete chemical inactivity around the molten metal.
- Controlled cooling atmosphere. The gas composition influences how the weld solidifies and what microstructure forms.
- Arc stability maintenance. Proper gas flow ensures consistent electrical conditions for stable welding.
What Happens Without Proper Gas Protection
- Porosity formation. Oxygen and nitrogen dissolve in molten metal, then form gas bubbles as it cools.
- Oxidation. Metal surfaces react with oxygen to form oxides that weaken the weld.
- Nitrogen pickup. Creates brittleness, especially problematic in stainless steel welding.
- Hydrogen embrittlement. Moisture in air breaks down to release hydrogen that causes cracking.
Gas Protection by Material Type
Carbon steel: Requires CO2 or Ar/CO2 mixes for proper wetting and penetration characteristics.
Stainless steel: Needs low-oxygen environments (Ar/CO2/He mixes) to prevent carbide precipitation.
Aluminum: Demands pure inert gases (Ar or Ar/He) due to high reactivity with oxygen.
Titanium: Requires complete inert protection including back purging due to extreme oxygen sensitivity.
Industry Standard
CORGON® 18
82% Ar / 18% CO2Why CORGON 18 excels for protection: The optimized argon/CO2 ratio provides excellent gas coverage while the CO2 component improves wetting and penetration in steel welding.
Flow rate for best protection: 12-15 L/min for most applications. Higher flow (18-20 L/min) needed in drafty conditions or for thicker materials.
⚠️ Critical for Weld Quality