Welding electrode with replaceable tip

1. Field of the Invention A resistance welding electrode that is particularly suited for resistance spot welding a workpiece to a substrate without cross-contaminating specific portions of the workpiece is described. This is done by sheathing an internal surface of the welding electrode with a thermoplastic polymeric material. Then, there is only contact between the welding electrode and the workpiece at the very distal end of the electrode adjacent to where the workpiece is to be connected to the substrate. Contamination in this area is not detrimental because subsequent workpiece plating does not take place there.