Which statement about slag is accurate?

• A. Slag forms to protect the weld and shield the arc.
• B. Slag accelerates the cooling of the weld and increases penetration.
• C. Slag is the welded metal that remains after deposition.
• D. Slag is only produced when using TIG welding.

Answer: (A)

Slag is the protective layer formed by the flux during welding, covering the molten weld bead and arc to keep air from causing oxidation as the metal cools. This protective role is why the statement is correct: slag forms to guard the weld and shield the arc while it solidifies. After welding, you chip away this slag to expose the clean weld metal beneath. Slag isn’t the deposited metal itself, and it’s not produced in TIG welding—which uses shielding gas instead of flux. It also doesn’t speed up cooling or increase penetration; those depend more on heat input and technique, while slag mainly provides protection during cooling.