Causes of porosity in TIG welds?

• A. Poor gas coverage, contamination, or drafts
• B. Excessive filler rod deposition
• C. Very fast travel speed
• D. Overheating the base metal

Answer: (A)

Porosity in TIG welds happens when the shielding gas that protects the molten metal from the atmosphere doesn’t do its job, so air gets trapped as the weld pool solidifies. The most common causes are poor gas coverage, contamination, or drafts. If the shielding gas blanket is thin, uneven, or interrupted—due to a too-large torch-to-work distance, incorrect flow rate, leaks in the gas supply, or an improper cup setup—the weld can trap gas pockets. Contamination on the workpiece or filler material, such as oil, grease, moisture, or dirt, introduces gases or oxides that form pores when heated. Drafts or air movement near the weld can blow away shielding gas, exposing the molten metal to air. In contrast, very fast travel speed changes heat input and bead shape but doesn’t directly create gas porosity, and overheating the base metal tends to cause oxidation or other defects rather than the porosity mechanism itself. Thus, poor gas coverage, contamination, or drafts best explain porosity in TIG welds.