Abstract: A process for producing thin walled coatings on elongated substrates by the electrostatic application of two superimposed layers of powder material is disclosed. The process comprises the steps of applying electrostatically a first layer of fusible powder material to an elongated substrate, at least partially fusing such first layer of powder material to provide a uniform coating on the elongated substrate, holding the at least partially fused coating at an elevated temperature below the full fusion temperature of the powder material to be applied as the second layer immediately prior to the application of such second layer, applying electrostatically a second layer of fusible powder material to the first layer, and fusing the total applied coating to achieve the desired coating thickness.

Abstract: An electrostatic fluidized bed coating unit is disclosed. The coating unit comprises a plenum chamber with means for ingress of a gas under a greater than atmospheric pressure, a porous plate located on top of the plenum chamber and extending to the limits of the containing walls of the plenum chamber, containing walls for powder immediately above the porous plate and forming essentially a continuation of the plenum chamber walls, a coating chamber secured to such powder containing walls, and an exhaust system for effecting a uniform fluidizing gas removal from an area essentially directly above the porous plate.