One requirement that must be known for choosing welding electrodes is the type of current that your welder uses for welding. Plain AC stick welders are very common but generally considered to be somewhat less powerful. Stick welders with both AC and DC capabilities are gaining popularity and can generally handle thicker materials in DC mode. For many home-shop welders the traditional 220-volt AC welder is more than capable of handling their needs and more. However, as in any hobby the lure of additional power is difficult to resist. The benefits of an AC/DC machine should not be overlooked in your decision-making, especially if your welding aspirations go beyond the amateur home shop realm.
AC current reverses its polarity 120 times per second and that cannot be changed. Because DC current flows in one direction it can be used as DC straight (shown as DC+ meaning electrode negative) or DC reversed (shown as DC- , electrode positive). Generally speaking DC- (electrode positive) welding yields roughly 10% deeper penetration than the same machine in DC- mode. The DC+ mode (electrode negative) has a higher deposit rate, the rod melts away faster and is deposited in the bead. Generally DC straight welds have medium penetration.
