What is a common cause of porosity in GMAW?

• A. Correct shielding gas quantity
• B. Inadequate gas shielding
• C. Excessive shielding gas
• D. No shielding gas

Answer: (B)

Porosity in GMAW occurs when the molten weld is not properly protected by shielding gas, allowing air to become trapped as the metal solidifies. Shielding gas acts as a blanket over the weld pool, keeping oxygen, nitrogen, and moisture out of the molten metal. When the shielding is inadequate—flow is too low, there are leaks in the gas supply, the nozzle is too far from the weld, or drafts blow the gas away—the protective layer isn’t there where it’s needed, and gas pockets form in the weld bead. To prevent this, verify the gas flow with the regulator, keep the torch close enough to maintain coverage, shield the work area from drafts, and ensure the gas line and hose are leak-free and the gas is dry. While no shielding gas would also cause porosity, the most common real-world issue is not providing enough shielding to fully cover the weld during deposition.