Arc Starting:

Generally , striking the arc is easier with DC, specifically if small diameter electrodes are used. With AC, the welding current passes through zero each half cycle, and this presents problems for arc beginning and arc stability.

Arc Length

Welding with a short arc length (low arc voltage) is simpler with DC than with AC. It is an significant consideration, except for the heavy iron powder electrodes. With those electrodes, the deep crucible made by the heavy covering automatically maintains the appropriate arc length while the electrode tip is dragged on the surface of the joint.

Arc Blow

On the other hand, current rarely presents a difficulty with arc blow because the magnetic field is continuously reversing (120 times per second). Arc blow might be a important problem with DC welding of ferritic steel due to unbalanced magnetic fields around the arc.