Gas contamination as low as 10 ppm moisture or 5 ppm oxygen can cause porosity, cracking, and oxidation in sensitive materials like aluminum and stainless steel. Industrial-grade gases (99.995% purity) are essential for critical applications, while commercial-grade may suffice for mild steel welding.
Gas Purity: Effects of Moisture, Oil, and Air Contamination
Types of Contamination and Effects
- Moisture (H2O). Creates hydrogen in the arc, leading to porosity and cold cracking in steel.
- Oxygen (O2). Causes oxidation, poor wetting, and inclusion formation in all metals.
- Nitrogen (N2). Creates brittleness, particularly problematic in stainless steel and aluminum.
- Oil vapors. Hydrocarbon contamination causes carbon pickup and irregular arc behavior.
Purity Requirements by Material
- Carbon steel: Commercial grade (99.9%) usually acceptable for most applications.
- Stainless steel: High purity (99.995%) required to prevent carbide precipitation.
- Aluminum: Ultra-high purity (99.999%) needed due to extreme oxygen sensitivity.
- Titanium: Laboratory grade purity essential, plus secondary purification sometimes needed.
Sources of Contamination
Cylinder handling: Damaged valves, contaminated fittings, or improper storage allow air infiltration.
Gas lines: Oil from compressors, moisture from humid air, or system leaks introduce contaminants.
Mixing equipment: Cross-contamination between different gases or poor mixing system maintenance.
Storage conditions: Temperature cycling can draw moisture into cylinders through micro-leaks.
High Purity
Linde CRONIGON® 2
99.995% Base PurityWhy purity matters for CRONIGON: Stainless steel welding requires ultra-clean gas to prevent carbide formation that destroys corrosion resistance—any contamination is permanent damage.
Purity verification: Linde provides certificates of analysis showing actual contamination levels, not just minimum specifications like generic suppliers.
🧪 Purity Critical