If root fusion is incomplete, which pass is used to help correct it?

• A. Filler pass
• B. Root pass
• C. Hot pass
• D. Cover pass

Answer: (C)

When the root fusion is incomplete, the goal is to re-melt and re-fuse the root area without adding unnecessary material. A hot pass does this: it’s a brief, high-heat pass run along the root that remelts the root bead and the joint interface to establish a continuous, sound fusion. This step targets the root region after the initial root pass and before or alongside filler passes, brushing away lack of fusion at the root. Filler passes add material to build up the weld but don’t specifically fix root fusion defects. The root pass is the initial attempt to establish the root, and the cover pass is the final layer to protect the weld; neither is intended to correct incomplete root fusion.