What is porosity in a weld and what are common causes?

• A. Porosity is gas pockets in weld metal; caused by moisture, oil or grease, surface contaminants, or inadequate shielding.
• B. Porosity is a measure of weld toughness.
• C. Porosity is the color of the weld bead.
• D. Porosity is the rate of filler metal deposition.

Answer: (B)

Porosity in a weld means there are gas pockets trapped in the weld metal as it solidifies. These voids form when gas gets into the molten pool and cannot escape before the metal hardens, which can weaken the joint and create points that may crack under stress or fatigue.

Common causes include moisture present on or in the metal, filler, or coatings; oil, grease, or other surface contaminants; and inadequate shielding, which lets atmospheric gases mix with the weld pool. Dirty or rusty surfaces, scale, and damp or contaminated welding consumables can also introduce gas into the weld. Proper cleaning, drying, and stable shielding are key to preventing porosity.

Porosity is not a measure of weld toughness, nor is it about the color of the weld bead or the rate of filler metal deposition.