Hi BM146,

A scratch start may be used in lieu of a high frequency start, and although the tungsten is briefly scratched against the work piece, there is the possibility of tungsten contamination. The arc should not be struck on a carbon block because of the likelihood of carbon contamination. Some codes do not allow scratch starts.

Hi BM146 ,

With scratch start the tungsten does get contaminated . When you use higher currents the tungsten will lose its ground point also with scratch start assuming the power source does not have the lift arc facility !