Abstract: An apparatus/method for detecting contamination during welding is disclosed. In one embodiment, contamination is detected during the welding of overlapping metal portion used in the production of can bodies. The apparatus monitors the voltage supplied to a welding electrode during welding. When the voltage increases above a predetermined level, which may indicate the presence of contamination, the electrical energy is directed away from the welding roller before the rollers pass the area of contamination. The diverted electrical energy is directed to a short circuiting device, such as a parallel combination of silicon control rectifiers. As such, the electrical energy may be directed away from the welding rollers to prevent damage to the rollers.