A piston rod has a hollow section with an open end, a housing, and a fastening connection for a piston. The housing includes a cap welded to the open end, a tubular intermediate piece welded to the cap, and a bottom part attached to the fastening connection. The cap has a shoulder received in the intermediate piece to form an annular space which functions as a labyrinth seal to receive any weld spatters formed during the friction welding process. The outside surface of the piston rod is machined to final dimensions and surface coated following welding.