ANS:B - prevent electrode from contamination.

The coating provided on the electrodes used in arc welding is not expected to add alloying elements. The purpose of the coating on welding electrodes, often referred to as flux, is primarily to:

1. Stabilize the arc: The flux coating helps to stabilize the arc by providing a consistent environment around the electrode tip. This aids in maintaining a steady welding process.
2. Prevent electrode contamination: The flux coating acts as a barrier, protecting the molten weld pool and the electrode from atmospheric contamination such as oxygen and nitrogen. This helps prevent defects in the weld, such as porosity.
3. Provide a protective atmosphere: The flux coating also generates a protective gas shield around the weld, which helps prevent atmospheric gases from reacting with the molten metal. This shield reduces the risk of oxidation and other undesirable reactions that could weaken the weld.

However, the coating on welding electrodes typically does not add significant alloying elements to the weld. While some specialized electrodes may contain alloying elements designed to enhance specific properties of the weld, the primary function of the flux coating is not to introduce alloying elements into the weld metal. Therefore, the coating provided on electrodes used in arc welding is not expected to add alloying elements.