Resistance welding involves the generationof heat by passing current through the resistance caused by the contact betweentwo or more metal surfaces. Small pools of molten metal are formed at thewelding area as high current (1000-100,000A) is passed through the metal.

Spot welding is a popular resistancewelding method used to join overlapping metal sheets for up to 3mm thick.

Two electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. The advantage of the method include efficiency energy use, limited workpiece deformation, high production rates, easy automation, and no required filler material. Weld strength is significantly lower than with other welding methods,making the process suitable fo rmany applications. It is used extensively in the automotive industry, ordinary cars have several thousand spot welds made by industrial robots. A specialized process, called shot welding, can be used to spot welding stainless steel.

Like spot welding, seam welding relies on two electrodes to apply pressure and current to join metal sheets. However,instead of pointed electrodes, wheel shaped electrodes roll along and often feedthe workpiece, making it possible to make long continuous welds. In the past,this process was used in the manufacturer of beverage cans, steel drums and anyround shape workpieces.