The invention relates to a device for treating surfaces of objects with rounded cross sections and at least one partially electrically conductive outer wall, comprising a plurality of treating stations; and a feed device including support devices for supporting objects to be treated, wherein the feed device is configured to transport the objects supported by a respective support device in a timed sequence from one treating station to another treating station, wherein one of the treating stations is a test station and includes a voltage source, an electrode coupled with the voltage source and a processing unit, wherein the processing unit is configured to detect voltage changes between the electrode and a respective object disposed at the respective test station. The invention also relates to an accordingly configured test station for a device for treating surfaces of objects with rounded cross sections and at least one partially electrically conductive outer wall and to a method for treating surfaces of objects with rounded cross sections and at least one partially electrically conductive outer wall.