What is the primary reason for cleaning the workpiece before welding?

• A. To improve appearance.
• B. Remove oils, paints, coatings to prevent porosity, explosions; ensure good weld quality and reduce fumes.
• C. To cool the metal before welding.
• D. To remove rust only.

Answer: (B)

Cleaning the workpiece is about removing anything that can contaminate the weld and create safety hazards. Oils, greases, paints, coatings, and other residues can burn, vaporize, or release gases as the metal melts, leading to porosity — tiny gas pockets that weaken the weld — and poor fusion. These contaminants can also produce fumes or flash fires, increasing the risk in the shop. By cleaning, you expose a clean metal surface that allows proper fusion, reduces the chances of gas entrapment, and lowers hazardous fumes. Removing rust alone isn’t enough because other contaminants like oil, grease, paint, and coatings still cause porosity and safety issues.