What is a common effect of using contaminated welding wire?

Using contaminated welding wire can lead to poor arc stability during the welding process. Contaminants on the wire, such as oil, rust, or dirt, can interfere with the smooth delivery of current and gas, which in turn affects the consistency of the arc. When the arc becomes unstable, it may flicker or extinguish intermittently, leading to inconsistent weld quality, increased spatter, and potential defects in the weld bead.

In the context of the other options, increased penetration, decreased spatter, and improved speed are not direct effects of contaminated welding wire. In fact, contamination typically has the opposite effects: it could reduce penetration due to inconsistent heat distribution, increase spatter due to erratic arc behavior, and slow down the welding process as the welder may need to adjust settings or rework welds that did not turn out correctly. Thus, the primary focus should be on the impact of contamination leading to poor arc stability.