What is the consequence of leaving contaminants on base metal before TIG welding?

• A. Porosity and inclusions occur
• B. Increased weld strength
• C. Faster welding
• D. No effect

Answer: (A)

Cleanliness of the base metal is crucial in TIG welding. If oil, grease, rust, dirt, or moisture are left on the metal, they can outgas or react when the weld pool forms. The shielding gas protects the molten metal from the atmosphere, but contaminants can still generate gas pockets (often hydrogen from moisture or hydrocarbons) and oxide films that get trapped as the metal solidifies. Those trapped gases and oxides become porosity and inclusions, weakening the weld. So the consequence of leaving contaminants is porosity and inclusions in the weld. Contaminants don’t improve strength or speed welding, and they do have a negative effect on weld quality.