Abstract: A corona treating apparatus has an electrically conductive electrode housing with a downwardly opening channel, within which are adjustably positioned a number of conductive electrode segments. Each segment has a stem which extends into the channel, and a foot which extends below the channel and which overlies an electrically conductive electrode roller, over which the material to be treated travels. Top springs extend into bores in the top of the electrode segments, and ball detents extend through the housing to urge against slots on one side of the segments. Each electrode segment stem has a first lip which engages with an upper ledge when the segment is in a retracted position, and a second lip which engages with a lower ledge on the opposite wall when the segment is in an active position. Pushing upwardly on one sideward flange of an electrode foot readily changes the position of each segment.