A power grid for a fluidized bed for electrostatically depositing a powdered plastic coating material from the bed onto an elongated metal substrate moving in a path of travel above the upper surface of the bed on a substantially horizontal pass line. The power grid includes two co-planar wire mesh elements positioned beneath the surface of the bed, the elements having opposed edges in parallel spaced relationship and defining a gap therebetween beneath the pass line. The edges are upturned to form a plurality of electrode segments, the tips of the electrode segments being substantially coincident with the upper surface of the bed when energized. In operation the electrode segments form a row of localized corona discharges to either side of the passing substrate to effect electrostatic deposition of a thin uniform film coating of the powdered material thereon.