Which gas is primarily used to prevent oxidation during brazing?

The correct answer is nitrogen, which plays a crucial role in preventing oxidation during brazing processes. Brazing involves the joining of metals using a filler material at elevated temperatures, and oxidation can pose a significant risk as it forms undesirable oxides on the metal surfaces. These oxides prevent effective bonding between the base metals and the filler.

Nitrogen is often used as a shielding gas during brazing because it is inert, meaning it does not react with the metals being joined or the brazing filler material. By displacing the atmospheric air in the brazing environment, nitrogen helps to create a protective atmosphere that minimizes oxygen's presence. This effectively reduces the chance of oxidation occurring on the metal surfaces, leading to a stronger and more reliable joint.

In contrast, argon is another inert gas commonly used in various welding and brazing applications, but it is less effective than nitrogen in certain conditions where the prevention of oxidation is critical. Oxygen is actually detrimental in this context, as it promotes oxidation, and carbon dioxide can also contribute to oxidation rather than prevent it. Therefore, nitrogen is the best choice for creating a non-reactive atmosphere that guards against oxidation during brazing.