Which of the following is NOT a common cause of porosity?

• A. Contaminants
• B. Moisture
• C. High travel speed
• D. Improper shielding gas coverage

Answer: (C)

Porosity in a weld comes from gas getting trapped in the molten metal as it solidifies. This gas usually comes from surface contaminants, moisture, or problems with the shielding gas. Oil, grease, rust, paint, or other contaminants on the workpiece or filler material release gases when melted, forming pores. Moisture on the surface or in the electrode/filler also releases hydrogen or other gases into the weld pool. If shielding gas coverage is inadequate or there are leaks or drafts, air can enter the weld zone and create gas pockets.

High travel speed, on the other hand, mainly changes heat input and the weld bead shape, and is more commonly linked to lack of fusion or excessive reinforcement rather than porosity. So the option that is not a common cause of porosity is high travel speed.