Abstract: Apparatus and method for treating the interior surfaces of hollow plastic objects to improve their adherency to and compatibility with another component, such as polyurethane foam. The invention consists of creating a vacuum in the object and drawing a conductive gas inside the object. A pair of electrodes are spaced apart from each other, and a source of electricity is provided thereto of sufficient intensity to produce an electrical discharge across the gap between the electrodes when an object is in the gap between the electrodes. The electrodes are arranged with regard to the size and configuration of the object to provide ionization of the conductive gas inside the object to surface treat the inner walls.