A sign that shielding gas may be contaminated is what weld appearance?

• A. Welds turn gray or sooty
• B. Welds are shiny and clean
• C. Weld beads flatten
• D. Welds glow green

Answer: (A)

Shielding gas keeps the arc and molten metal from reacting with air. When that shield is compromised by moisture, oxygen, or other contaminants, the weld surface oxidizes and deposits impurities as it cools. That oxidation and impurity buildup appear as a dull gray, sometimes sooty-looking bead instead of a bright, clean finish. So a gray or sooty weld is a clear sign the shielding gas isn’t doing its job. A shiny, clean weld means the shield is effective, while beads that flatten point to issues with heat or travel speed rather than gas quality. A green glow isn’t a standard indicator of gas contamination. To prevent this, check for leaks, allow proper purge time, use fresh, dry shielding gas, and keep hoses and fittings clean.