What must be done to a welded joint if it must be rewelded?

• A. All traces of the old weld must be removed so the new weld will penetrate the base metal.
• B. Grind and re-weld
• C. Apply new weld over old weld
• D. Scrub with solvent

Answer: (A)

When a welded joint must be rewelded, the old weld material has to be removed completely so the new weld can fuse with clean base metal. Any remaining old weld can prevent full penetration into the base metal, creating a weak joint with possible lack of fusion, porosity, or cracks. Old weld metal and the surrounding heat-affected zone may contain contaminants or altered microstructure that undermine the repair, so gouging or grinding it out exposes sound metal for a proper bond. Solvent cleaning won’t remove metal, and welding over or partially grinding the old weld can trap defects. Removing all traces of the old weld sets up the best conditions for a sound, properly fused repair.