What is a common cause of weld porosity?

• A. Clean metal surfaces
• B. Contaminated metal or improper shielding gas flow
• C. Proper shielding gas flow
• D. Rapid cooling

Answer: (B)

Weld porosity happens when gas gets trapped in the weld metal as it cools, leaving small holes that weaken the joint. The most common cause is contamination on the metal surface or problems with shielding gas flow. If the metal has oil, grease, dirt, rust, or moisture, those contaminants release gases into the molten pool and form bubbles. Likewise, if the shielding gas isn’t flowing properly—low flow, leaks in the hose or bad gas mix—the protective atmosphere isn’t keeping out atmospheric gases, so gas pockets form as the weld solidifies. Keeping the metal clean and dry and ensuring a proper, continuous shielding gas flow are key to preventing porosity. Rapid cooling can lead to other defects, but it isn’t the primary cause of porosity.