What are common causes of porosity?

• A. Contaminants, moisture, improper shielding gas coverage, and fast cooling
• B. Proper cleaning and dry environments
• C. Excessive welding speed and cold surroundings
• D. Large filler metal diameter only

Answer: (A)

Porosity happens when gas gets trapped in the weld metal as it solidifies. The most common culprits are things that release gas or interfere with shielding during welding. Contaminants on the surface or in the weld area—oil, grease, solvents, paint, rust, or scale—outgas when heated and can form gas pockets in the molten metal. Moisture in base metal, in coatings, or on the electrode also produces hydrogen gas as the weld is made. Shielding gas coverage is essential; if shielding is inadequate due to leaks, insufficient flow, improper torch or nozzle setup, or drafts, air can invade the weld area and introduce gas that becomes porosity. Finally, if the metal cools too quickly, dissolved gases have less time to escape and are more likely to be trapped as the weld solidifies. Keeping surfaces clean and dry, ensuring proper shielding gas coverage, and controlling heat input and cooling help prevent porosity.