Abstract: A separable connector module of the fault-actuated piston type comprises an aluminum container tube, a bore contact member within the container tube, and a piston for actuating the bore contact member in response to closing on a fault. The piston is primarily of copper but has a thin coating of dissimilar metal on its exterior. A sleeve of copper tightly fitting with the container tube acts as a cylinder for receiving the exterior of the piston in contacting relationship between copper and said dissimilar metal. The sleeve has adjacent one end an integrally formed end wall containing a central opening, and a copper-alloy nut is brazed to the end wall adjacent the central opening.