A common cause of weld porosity?

• A. Contaminated metal or improper shielding gas flow
• B. Excessive heat
• C. Too fast travel speed
• D. High voltage

Answer: (A)

Weld porosity happens when gas bubbles become trapped in the weld metal as it cools, leaving small voids or pores in the bead. The shielding gas is meant to blanket the molten metal and keep air from contaminating it. If the shielding gas flow is too low, there’s a leak, or the gas is contaminated, air can invade the weld pool and form pores. Contaminants on the metal surface—such as oil, grease, paint, rust, or moisture—also release gases when heated and contribute to porosity.

In practice, the most common fixes focus on cleanliness and the shielding gas system: clean and dry the metal thoroughly, remove oils and coatings, and ensure the shielding gas supply is correct, with proper flow and leak-free connections, and that you purge the line before starting. The other factors listed affect bead shape or heat input more than porosity itself, so they are less likely to be the primary cause of porous welds.