What is porosity?

• A. Gas pockets trapped in the weld metal that reduce strength and integrity.
• B. Nonmetallic slag trapped within the weld metal due to improper slag control.
• C. An opening at the root due to insufficient fusion.
• D. A crack that propagates through the weld.

Answer: (A)

Porosity is gas pockets trapped in the weld metal as it solidifies. These tiny voids form within the weld bead and create weaknesses because they reduce the effective cross‑section of metal and can act as stress risers, making the weld more prone to cracking or failure under load. Porosity typically shows up as small holes or voids in the deposited weld metal and can result from contamination (oil, grease, rust, moisture), improper shielding (air slipping in during welding), or hydrogen entrapment (wet electrodes or damp environment). It’s different from slag inclusions, which are nonmetallic materials trapped inside the weld, from lack of fusion at the root, or from cracks, which are fractures in the weld.