What are the two categories of shielding gas used in MIG welding?

In MIG welding, the two categories of shielding gas are reactive and inert gases. Inert gases, such as argon and helium, do not chemically react with the weld material, providing a stable and clean environment that helps to protect the weld pool from contamination. This is crucial for achieving high-quality welds, especially when working with materials like aluminum and stainless steel. Reactive gases, on the other hand, might include mixtures that contain CO2 or other active components. These gases can participate in reactions during the welding process, which can influence the characteristics of the weld. For example, adding a small percentage of carbon dioxide in a mix with argon can improve the arc stability and deposition rate, making it beneficial for certain applications.

The other categories presented in the options—like oxidizing and reducing—are not specifically related to MIG welding, as they denote different types of chemical reactions rather than practical classifications of shielding gases. Similarly, terms like clean and dirty or cheap and expensive do not accurately describe the functional roles that shielding gases play in the welding process. Understanding the roles of reactive and inert gases is essential for ensuring the effectiveness and quality of MIG welding.