LA City Certified Welder Written Practice Test

E7018 is a low-hydrogen SMAW electrode that needs a stable arc and adequate heat input to activate its flux and weld cleanly. Using it with alternating current or with direct current where the electrode is positive (reverse polarity) provides that stable arc and sufficient heat to properly deposit the weld and dehydrate the coating. With electrode negative (DC-), the arc characteristics shift in a way that can reduce heat in the weld pool and affect bead quality and hydrogen control for this electrode. Among the common practice options, AC with reverse polarity gives reliable arc stability and weld quality for E7018, which is why that choice is the best fit.