CO2 dissociates in the welding arc into CO and atomic oxygen, creating controlled oxidation that improves wetting and penetration but increases spatter and requires deoxidizers in the wire. This dissociation process fundamentally changes how heat transfers through the arc.
CO2 Dissociation: Oxidation and Heat Transfer Effects
The Dissociation Process
- Arc heat breaks down CO2. At arc temperatures (>6000K), CO2 splits into CO + O.
- Oxygen reacts immediately. Atomic oxygen oxidizes metal droplets and weld pool surface.
- CO formation increases heat transfer. Carbon monoxide molecules carry more energy than inert gases.
- Recombination on cooling. CO and O recombine to CO2 as temperatures drop.
Effects on Weld Characteristics
- Deeper penetration. Enhanced heat transfer and arc constriction drive deeper into base metal.
- Improved wetting. Mild oxidation cleans the weld pool surface for better flow.
- Higher spatter levels. Violent reactions in metal droplets cause more spatter than inert gases.
- Requires deoxidizers. Wire must contain silicon and manganese to remove oxygen from weld metal.
CO2 Percentage Impact
100% CO2: Maximum penetration and lowest cost, but rough arc and high spatter.
75-80% Ar / 20-25% CO2: Good penetration with reduced spatter, industry standard for thick steel.
90-95% Ar / 5-10% CO2: Smooth arc with moderate penetration, ideal for thin materials.
98% Ar / 2% CO2: Minimum CO2 for steel welding, very low spatter but reduced penetration.
Balanced Performance
CORGON® 18
82% Ar / 18% CO2Why 18% CO2 works optimally: Provides significant penetration benefits from CO2 dissociation while maintaining good arc stability from the argon base.
Best applications for CORGON 18: General structural steel fabrication, 3-25mm thickness range, both single and multi-pass welding.
⚗️ Chemical Process