Which control begins the flow of shielding gas before the arc starts?

• A. Pre-Flow Control
• B. Arc Initiation Control
• C. Gas Flow Start
• D. Shielding Gas Start

Answer: (A)

Starting the shielding gas flow before striking the arc is essential to purge air from the joint and establish a protective gas envelope right as welding begins. This pre-flow control does exactly that: it begins the shielding gas flow ahead of ignition so the weld area is already shielded the moment the arc is struck. That pre-purge helps prevent contamination like oxidation and porosity and sets up a stable environment for the arc and molten metal. After ignition, gas continues for a post-flow period to maintain shielding as the weld cools. Other options would initiate gas flow at or after ignition, which can allow air to enter the weld area during the critical moment of arc initiation.