Which of the following is a welding defect that can cause rejection?

• A. Over-weld
• B. Porosity
• C. Smooth surface finish
• D. Adequate penetration

Answer: (B)

Porosity is a welding defect that can cause rejection. It means gas pockets are trapped in the weld metal as it cools, creating voids that weaken the joint. These voids can reduce tensile strength, fatigue resistance, and corrosion performance, and inspectors often reject welds with porosity because the flaw indicates contamination or shielding failures during welding. Porosity is typically caused by moisture or oil on the material or electrode, rust or dirt, poor shielding gas coverage, or welding too quickly, all of which allow atmospheric gases to become trapped in the molten weld. In contrast, a smooth surface finish and adequate penetration are signs of good weld quality, not defects, and an over-weld is excess material that can cause distortion or waste, and is only a defect if it violates reinforcement limits.