Which is a common weld quality issue that reduces joint integrity?

• A. Porosity
• B. Cratering only
• C. Spatter only
• D. Undercutting only

Answer: (A)

Porosity is a common weld quality issue that reduces joint integrity. It means tiny gas pockets become trapped in the weld metal as it cools, which lowers the effective cross‑section and creates stress risers. Those voids weaken the weld and can become initiation points for cracks under load, reducing strength and fatigue life in bridge joints. Porosity typically stems from insufficient shielding, moisture or contamination, or improper welding parameters, making it a frequent and impactful defect.

Other defects like cratering at the end of a weld, spatter on the surface, or undercutting at the weld toe can affect quality too, but they don’t impact the joint integrity as broadly or consistently as porosity does. Cratering can cause localized cracking if severe, spatter is mostly cosmetic, and undercutting reduces throat thickness and can be a fatigue concern, but porosity directly compromises the weld’s overall strength and durability.