Carbon Dioxide

Overview

Carbon dioxide (CO₂) is a colorless, odorless gas that plays a crucial role in various industrial applications. As a naturally occurring compound, CO₂ is widely produced through combustion processes, fermentation, and industrial chemical reactions. It is used in applications ranging from welding and metal fabrication to cleaning, refrigeration, and chemical processing. Unlike inert gases such as argon and nitrogen, CO₂ exhibits mild reactivity under certain conditions, making it a versatile and cost-effective choice for numerous industries.

CO₂ as a Welding Gas

In welding, carbon dioxide is commonly used as a shielding gas, particularly in gas metal arc welding (GMAW), also known as MIG welding. Shielding gases serve to protect the weld pool from atmospheric contamination, preventing oxidation and porosity in the finished weld. (See NOTE below)

Pure CO₂ vs. CO₂ Blends

  • Pure CO₂ is widely used in carbon steel welding due to its affordability and deep penetration capability. Unlike inert gases such as argon, CO₂ is semi-reactive, meaning it interacts with the welding arc to enhance heat transfer. This results in a hotter arc, deeper penetration, and increased weld strength. However, pure CO₂ tends to produce more spatter and a rougher bead appearance compared to argon-based mixtures.
  • CO₂-Argon Blends (e.g., 75% Argon / 25% CO₂) are often preferred for improved arc stability and reduced spatter while still retaining CO₂’s penetration benefits. These blends are used in applications requiring better weld aesthetics, lower heat input, and reduced post-weld cleaning.

Advantages and Considerations

  • Deep weld penetration makes CO₂ an excellent choice for thicker materials.
  • Low cost compared to inert gases like argon or helium.
  • Increased spatter production, requiring additional cleaning and post-processing.
  • Limited use in non-ferrous metals—CO₂ is generally not suitable for aluminum or stainless steel welding without modifications.

CO₂ as a Blasting Medium

CO₂ is also used in abrasive blasting, commonly referred to as dry ice blasting. Unlike traditional abrasive media such as aluminum oxide or glass beads, CO₂ blasting uses solid CO₂ pellets (dry ice), which sublimate upon impact, leaving no secondary waste.

Dry Ice Blasting Process

Dry ice blasting involves accelerating CO₂ pellets at high velocity onto a surface to remove contaminants, coatings, or residues. Upon impact, the cold temperature (-78.5°C or -109.3°F) causes thermal shock, cracking and loosening surface debris. The solid CO₂ then sublimates directly into gas, leaving behind no cleanup materials other than the removed contaminants.

Key Applications

  • Industrial Equipment Cleaning – Used in power plants, food processing facilities, and pharmaceutical industries to remove grease, residues, and contaminants without abrasion.
  • Historical and Delicate Surface Restoration – Effective for removing paint, soot, and biological growth from stone, brick, and wood without damaging the substrate.
  • Automotive and Aerospace Maintenance – Used for cleaning molds, engines, and electrical components without moisture or abrasive impact.
  • Electronics and Electrical Equipment – Safe for cleaning switchgear, circuit boards, and other delicate components without the risk of conductive residue.

Advantages and Considerations

  • Non-abrasive – Preserves surface integrity and is ideal for delicate or precision equipment.
  • No secondary waste – Eliminates the need for post-blasting cleanup.
  • Eco-friendly – Reduces chemical and water usage in industrial cleaning.
  • Higher equipment cost – Requires specialized blasting equipment and dry ice storage.

Other Industrial Uses of CO₂

Beyond welding and blasting, CO₂ has various other industrial applications:

  • Refrigeration and Cooling (Cryogenic Freezing) – Used in food preservation and industrial cooling systems.
  • Chemical Processing – Serves as a solvent in supercritical CO₂ extraction for pharmaceuticals and food industries.
  • Fire Suppression – CO₂ extinguishers are widely used for electrical and liquid fires.
  • Carbonation – Common in beverage production to create fizzy drinks.

Conclusion

Carbon dioxide is a highly versatile industrial gas with applications in welding, blasting, refrigeration, and chemical processing. As a welding gas, it provides cost-effective shielding, deep penetration, and strong welds, particularly for carbon steel applications. In dry ice blasting, CO₂ offers a non-abrasive, eco-friendly alternative to traditional media, making it ideal for delicate, residue-free cleaning. Its ability to sublimate without leaving secondary waste makes it particularly useful in environments where cleanup is a concern. Whether used in fabrication, maintenance, or surface treatment, CO₂ continues to be an invaluable resource across multiple industries.

NOTE:

In some countries, particularly in Europe, the use of carbon dioxide (CO₂) as a shielding gas in welding falls under the MAG (Metal Active Gas) welding designation rather than MIG (Metal Inert Gas). The distinction arises because CO₂ is not entirely inert; it actively influences the welding process by reacting with the molten metal, affecting penetration, arc characteristics, and spatter levels.

MAG welding refers to processes where active gases, such as CO₂ or oxygen-enriched argon blends, contribute to chemical interactions in the weld pool. In contrast, MIG welding strictly involves inert shielding gases like argon or helium, which do not react with the weld metal. The MAG process is widely used for welding carbon and low-alloy steels, where CO₂ or CO₂-argon blends provide a balance between cost, penetration depth, and weld quality.

This distinction is important for welders operating under ISO, EN, or European welding standards, as process terminology differs from that commonly used in North America, where both MAG and MIG welding are generally grouped under GMAW (Gas Metal Arc Welding).