Abstract: A process for applying a coating of plastic material to a metal tube of finite length having a pretreated surface by applying plastic coating materials on the metal tube in a direction horizontal and perpendicular to its direction of travel, the process being characterized by the following sequence of steps:(a) heating a fixed metal tube to a temperature above the melting point of the plastic material to be employed;(b) causing a mixture of plastic powder and air to pass through the metal tube whereby the plastic material is fritted onto the inside surface of the tube;(c) thereafter rotating the metal tube and applying to the exterior surface thereof in a plurality of stages a plastic material, said plastic material being electrostatically sprayed onto the rotating metal tube; and(d) after each stage of electrostatically applying plastic to the outside surface of the metal tube and applying plastic material to the inside surface thereof, completely melting and smoothing the plastic material.

Abstract: A method of and apparatus for the surface cleaning of workpieces, e.g. the degreasing, scale-removal and rust removal from a metallic surface, especially so as to produce a bright, clean and relatively smooth surface to receive a coating, positions the workpiece in a fluidized bed of an abrasive, such as particle of corundum or quartz sand, and directs fine jets of gas at the surface from nozzles spaced therefrom within the fluidized bed.

Abstract: A method of coating metal pipes externally with a uniform thin coating of a synthetic resin, such as a polyamide, polyethylene or polyvinyl chloride, which comprises heating the pipe to a temperature to enable a frit of discrete particles to bond to a pipe in a chamber through which the pipe is passed and which is charged with a mixture of a gas and the particles. Thereafter the frit is smoothed by heating the pipe to a higher temperature as it leaves the chamber to cause the particles to coalesce.This is a continuation of application Ser. No. 616,314, file 24 Sept. 1975 and now abandoned.

Abstract: An apparatus for externally coating elongated metal members and, particularly, endless metal tubing with synthetic-resin using a powder-melt process in which the powder is initially fused to the surface of the metal member and concurrently or subsequently caused to coalesce into a coating film. The metal member is passed through a fluidized bed of the synthetic-resin powder after being preheated and the powder is induced to flow along the metal member through an annular nozzle formed on a coating head within the fluidized bed. The powder is advantageously sucked through the coating head and is drawn via the annular nozzle into contact with the metal member.

Abstract: Hollow bodies, e.g. pipes, are coated with protective layers of a liquid or pulverulent material by electrostatic spraying and hardening in which the bodies are disposed horizontally and parallel to one another upon a chain conveyor and are automatically displaced transverse to their longitudinal axes. In a first stage the coating is provided on the hollow bodies exclusively of their end regions and in a second stage the coatings are applied to the end regions.

Abstract: A method of and an apparatus for the internal coating of ducts with a synthetic resin, especially long steel pipes or tubes, in which gas-entrained synthetic-resin particles are passed through the tube while the latter is heated progressively by displacing the tube relative to a surrounding induction-heating coil. Thereafter, a gas stream free from particles is used to clear the interior of the tube.