Canadian Standards Association (CSA) 178.2 Level 1 Practice Exam

Arc-start methods differ mainly in how they initiate the arc and how much wear or contamination they create on the tungsten electrode. The cost impact comes from consumables and maintenance: more electrode wear and more cleanup or rework mean higher ongoing costs.

When you start the GTAW arc by touching the electrode to the workpiece (or by a lift mechanism that briefly makes contact to strike the arc), the tungsten tip and sometimes the workpiece material can degrade quickly. This leads to faster electrode consumption, more frequent grinding or replacement of the tungsten, and potential weld contamination that requires extra cleaning or rework. Even though lift-start devices help avoid some issues of pure scratch starts, the fundamental contact during arc initiation still drives higher consumable and maintenance costs than the other methods.

Scratch start uses no dedicated start mechanism and keeps the electrode in the air until the arc forms, which keeps consumable costs down. Oscillating start and spot start are more about how the arc is established with control features, but they typically involve less direct electrode wear during initiation and don’t incur the same level of consumable replacement and post-weld cleanup as contact-based starts.

So, starting the arc with direct contact (or a lift-when-needed approach that relies on contact) tends to incur the highest ongoing costs due to electrode wear and the associated maintenance and cleaning needs.