Shielding Gas: What You Need Know

photo of a person doing welding work, for a blog about shielding gas

When it comes to welding, one of the quiet heroes behind clean, strong welds is the shielding gas. From working in a heavy fabrication shop to doing precision TIG work on aluminium, the right gas makes a big difference. 

This article walks you through what shielding gas is, why it matters, how it’s used in welding, and how to choose the right one, plus a look at our premium solutions like ARCAL™ that help welders in their work.

What Is Meant by Shielding Gas?

A shielding gas is an inert or semi-inert gas (or gas mixture) that envelopes the weld zone during arc welding, protecting it from air (oxygen, nitrogen, water vapour) that can damage the weld.
In simpler words: when you’re welding, molten metal is vulnerable, the surrounding air can cause oxidation, porosity and weak spots. A shielding gas creates a protective blanket so you get clean fusion and stronger joints.

Shielding Gas Purpose

The purpose of shielding gas boils down to one main objective: to protect the weld zone from atmospheric gases that would compromise integrity. That means:

  • preventing oxidation, nitriding or hydrogen uptake, all of which weaken welds.
     
  • assisting in arc ignition and stability.
     
  • controlling heat input and weld bead shape.
     
  • reducing defects and improving appearance and mechanical properties.
     

What Gas Is Used As a Shielding Gas?

There are several gases used as shielding gas, including:

  • Argon: A noble gas, widely used because it’s unreactive and gives a stable arc.
  • Helium: Also an inert gas; used especially for aluminium or thick sections where extra heat and a wide arc are helpful.
  • Carbon Dioxide (CO₂): Popular in MIG/MAG welding of steels; it gives good penetration but can cause more spatter.
  • Oxygen: Not typically used on its own as a shielding gas, but small amounts (1–5%) might be added to argon mixes to stabilize the arc or improve wetting.
  • Hydrogen/Nitrogen blends: Less common, used in specialized applications for improved penetration or mechanical properties.

What Is Shielding Gas in Welding?

In welding, processes like MIG welding (Metal Inert Gas) or TIG welding (Tungsten Inert Gas) depend on a shielding gas flowing over the weld pool and electrode. This gas shields the molten metal and the arc from atmospheric contamination.
Without it, you risk defects like porosity, weak fusion, oxidation of the weld metal, or compromised corrosion resistance (especially in stainless or exotic alloys).

Effect of Shielding Gas in Welding

The choice of shielding gas influences many weld characteristics:

  • Arc stability: An appropriate gas gives a stable arc, fewer disruptions, smoother weld bead.
     
  • Penetration and fusion: Some gases (or blends) provide deeper penetration and faster weld speeds.
     
  • Bead appearance: Spatter, bead width, heat-affected zone size, all affected by shielding gas selection.
     
  • Weld quality and defects: Incorrect gas can lead to porosity, oxidation, inclusions, and weakening of the weld.

Why Shielding Gases Are Used in Welding

Welding isn’t just about melting metal and letting it cool: you’re dealing with molten metal, high heat, and a reactive environment. Atmospheric air contains oxygen, nitrogen and water vapour, any of which entering the weld zone can cause serious issues (porosity, embrittlement, rust potential later). Shielding gases keep those intruders out, creating a stable, controlled environment for the weld.

How Can Shielding Gases Be Supplied?

Shielding gases are supplied in cylinders (or bulk tanks for large operations) equipped with regulators, flow meters, and in many cases a quick-connect system.
For example, Air Liquide offers the ARCAL™ range, ready-to-use shielding gas solutions engineered for different welding applications:

  • ARCAL™ Prime: Pure argon (99.998%) solution for most TIG, plasma and universal root shielding.
     
  • ARCAL™ Chrome: Mix designed for stainless steel MAG welding.
     
  • ARCAL™ Speed: Mix optimised for high travel speed and high deposition rate MAG welding of carbon steels.
     
  • ARCAL™ Force: Built for heavy use in large carbon steel structures, even under oxidized or contaminated surfaces.

All ARCAL™ cylinders come equipped with EXELTOP™, featuring an on/off lever, quick-connect system and permanent pressure gauge so you always know what’s in the cylinder.

Choosing the right shielding gas is essential for welders. Contact us at Air Liquide to discuss how our solutions can help you.

Frequently Asked Questions (FAQs)

What Does a Shielding Gas Do?

A shielding gas protects the weld from air, stabilizes the arc, and controls weld shape and penetration. Without it, you’re fighting the atmosphere instead of welding the metal.

Is Argon Used as a Shielding Gas?

Yes, argon is one of the most common shielding gases, especially in TIG and MIG welding of aluminium, titanium, copper alloys and even steel when purity and arc stability matter.

Is Oxygen a Shielding Gas?

Oxygen isn’t used alone as a shielding gas because it causes oxidation, but small amounts (1–5%) are added to argon or argon/CO₂ blends to stabilize the arc and improve weld flow.