Abstract: A modular galvanic current control resistor assembly for application to a metallic sheathed heating element of a domestic water heating tank to prevent heating element corrosion includes a circular metallic disc adapted to fit over the sheath ends of a U-shaped immersion heating element protruding in electrically insulated relationship through a metallic screw plug or the like mounting means used to affix the heating element to the tank, an electrically insulating gasket coextensive with the disc and a galvanic current control resistor having a pair of leads. The sheath ends of the heating element extend through the gasket and disc with portions of the disc around each sheath end crimped, compressed or friction fitted into electrical contact therewith.