US Patent 7323226 Tribostatic fluidised bed powder coating process

A process for forming a coating on a substrate, including the steps of effecting tribostatic charging of a body of powder by establishing a fluidised-bed of the body of powder in a fluidising chamber at least a part of which is conductive, applying a voltage to the conductive part of the fluidising chamber, immersing a substrate which is electrically non-conductive or poorly conductive, either electrically isolated or earthed, wholly or partly in the fluidised bed, withdrawing the substrate from the fluidised-bed and forming adherent particles of the powder into a continuous coating over at least part of the substrate.