Final answer:
In MIG welding, the consumable electrode is used not only to maintain the electric arc but also to contribute material to the weld joint. In contrast to sacrificial electrodes used for corrosion protection, the MIG welding electrode is melted and fused with the base materials to create a durable joint.
Step-by-step explanation:
The electrode used in MIG (Metal Inert Gas) welding serves as a consumable material that is melted during the welding process. This consumable electrode is fed continuously to the weld pool, where it not only helps to conduct the electric current needed to maintain the arc but also becomes part of the finished weld. This process is in contrast to the use of sacrificial electrodes in applications such as corrosion prevention for underground pipelines, where metals like magnesium are used as an anode in a galvanic cell to protect structures made of less reactive metals like steel. Unlike in corrosion protection scenarios where sacrificial anodes are deliberately oxidized to prevent the corrosion of another metal, in MIG welding, the electrode is intentionally consumed to add filler material to the joining metals.
In welding, the electrode's metal is chosen based on the metals being welded and the desired properties of the weld. For instance, electrodes with high manganese content might be used for welding high-strength steels. As the electrode melts, it combines with the base metals to form a solid joint upon cooling. The electrode in MIG welding, therefore, undergoes a transformation as it is consumed, contrasting with an inert electrode which merely transfers electrons in an electrochemical cell without undergoing any chemical transformation itself.