Which condition is indicated by root surface contamination, such as heavy oxide flakes?

• A. Excessive heat input
• B. Insufficient filler metal
• C. Excessive penetration
• D. Root surface contamination

Answer: (D)

Root cleanliness at the joint is essential for a sound TIG root pass. Heavy oxide flakes on the root surface signal contamination before welding. Oxide scales come from moisture, oil, grease, rust, or prior heat exposure and don’t weld well with the molten metal, preventing proper wetting and often causing porosity or lack of fusion at the root. This sign points directly to root surface contamination, so the fix is thorough cleaning of the root area—mechanical cleaning to remove oxide, degreasing, and ensuring the surface is dry—followed by maintaining clean, tight shielding gas coverage to prevent re-oxidation. The other issues—too much heat input, not enough filler metal, or too much penetration—show different symptoms and aren’t indicated simply by oxide flakes on the root.