A sealing device and method of making it for insulating and sealing a joint electrically connecting a wire or ribbon anode to an electrical cable. The cable is insulated except at an open region where the wire anode is connected to it. The sealing device comprises a body of an insulating material molded in situ about the electrical joint to completely cover it and bond to portions of the electrically insulating covering contiguous with the joint to thereby insulate the joint and prevent the ingress of water or other materials into the joint.