Which condition would necessitate pre-weld cleaning?

Which condition would necessitate pre-weld cleaning?

• A. Oil on metal surface.
• B. Metal is freshly zinc coated.
• C. Surface is dry and clean.
• D. Base metal has no rust.

Answer: (A)

Oil on the metal surface must be cleaned before welding because oil acts as a contamination that interferes with proper fusion. A greasy film prevents the molten filler metal from wetting and bonding to the base metal, and as it burns off during welding it can generate gases that form porosity and weaken the weld. If the surface is dry and clean, or rust-free, no extra cleaning is required beyond normal prep. A freshly zinc-coated surface introduces a coating that typically needs special handling, but the clear, immediate reason that requires pre-weld cleaning in this scenario is the presence of oil.

Oil on the metal surface must be cleaned before welding because oil acts as a contamination that interferes with proper fusion. A greasy film prevents the molten filler metal from wetting and bonding to the base metal, and as it burns off during welding it can generate gases that form porosity and weaken the weld. If the surface is dry and clean, or rust-free, no extra cleaning is required beyond normal prep. A freshly zinc-coated surface introduces a coating that typically needs special handling, but the clear, immediate reason that requires pre-weld cleaning in this scenario is the presence of oil.