What polarity is typically used for gas metal arc welding with solid wire?

In gas metal arc welding (GMAW), commonly known as MIG welding, reverse polarity is typically used when welding with solid wire. Reverse polarity refers to the configuration where the electrode is positively charged and the workpiece is negatively charged. This setup is beneficial because it allows for deeper penetration into the base metal and results in a more fluid weld pool, which is critical for achieving a strong and well-finished joint.

In reverse polarity, the heat generated during the welding process is concentrated at the workpiece rather than the electrode. This means that more of the heat is utilized for melting the base metal, which is especially useful for welding thicker materials. Additionally, the increased heat can improve arc stability and reduces the risk of porosity in the weld, making it easier to achieve high-quality welds.

Using straight polarity, alternating current, or direct polarity does not provide the same benefits related to penetration and weld pool fluidity that reverse polarity does, which is why reverse polarity is preferred for solid wire in MIG welding.