Resistance spot welding is used extensively to join strip steels during car body assembly. Strip steels typically have low C_equiv values and are therefore relatively easily welded. Problems can arise for pre-painted strip and zinc coated strip. Resistance spot welding involves the two parts being clamped together between two electrodes and a large electric current being passed through them. The material between the electrodes heats up, yields and is squeezed together. It then melts, destroying the interface between the parts. The current is switched off and the 'nugget' of molten material solidifies forming the joint.