Back purge uses what type of gas?

Back purge uses what type of gas?

• A. Inert gas
• B. Oxygen
• C. Air
• D. CO2

Answer: (A)

Back purge protects the weld root from exposure to air by flooding the backside with a non-reactive atmosphere. The goal is to keep oxygen (and other reactive gases) away from the molten metal so oxidation, discoloration, and unwanted metallurgical changes don’t form. An inert gas, such as argon (often used in practice), provides this shield because it doesn’t react with the metal or the molten pool. Using oxygen, air, or CO2 would not provide that protective, non-reactive environment and would promote oxidation and related defects. Therefore, the gas used for back purge is inert.

Back purge protects the weld root from exposure to air by flooding the backside with a non-reactive atmosphere. The goal is to keep oxygen (and other reactive gases) away from the molten metal so oxidation, discoloration, and unwanted metallurgical changes don’t form. An inert gas, such as argon (often used in practice), provides this shield because it doesn’t react with the metal or the molten pool. Using oxygen, air, or CO2 would not provide that protective, non-reactive environment and would promote oxidation and related defects. Therefore, the gas used for back purge is inert.