With ____, lack of cleanliness may cause the weld pool to show overheating and poor gas coverage.

• A. Aluminum
• B. Stainless steel
• C. Low carbon steel
• D. Mild steel

Answer: (B)

Stainless steel is especially sensitive to surface cleanliness because it forms a stable oxide film and readily retains contaminants. If the surface isn’t thoroughly cleaned, oil, grease, fingerprints, and oxide scales remain and disrupt how the shielding gas protects the weld pool. That disruption lets oxidation occur near the pool and makes the gas coverage seem poor, often accompanied by an appearance of overheating in the weld bead. Thorough cleaning removes oil and oxide and helps the shielding gas establish a continuous protective envelope, preserving proper wetting and heat distribution. In practice, clean stainless steel surfaces with appropriate solvents, scrub with a stainless-steel brush, and handle with clean gloves to avoid recontamination, then proceed with welding to achieve better gas coverage and avoid overheating signs.