Which of the following statements best identifies a root defect in GTAW?

• A. Porosity and Cracks
• B. Incomplete Fusion and Concave Root Surface
• C. Slag Inclusions and Porosity
• D. Grapes and Porosity

Answer: (B)

Root defects are problems at the weld joint where the weld metal must fuse with the base metal at the root. Incomplete fusion at the root means the weld metal didn’t fully bond to the base metal along the root, leaving a weak area. A concave root surface shows underfilling at the root—the bottom of the weld is sunken rather than properly filled—another clear sign of poor root fusion or penetration. Together, these two indicators specifically point to problems at the root of the weld, which is why this option best identifies a root defect in GTAW. Other choices mention porosity or slag in ways that aren’t specific to the root, or bring up terms not typical for GTAW, so they don’t identify root defects as clearly.