Applying protective coating to metal pipe surfaces - simultaneously using metal evaporator and metallisation element for external and internal surfaces.

摘要

Protective coatings are applied to the internal and external surfaces of metal pipes by disposing metallising agent in the interior of each pipe and advancing each pipe through a vacuum chamber. The pipes are rotated and their external surface is coated using a metal evaporator. The heat of the pipes during the metal coating operation causes melting of the metallising agent to provide simultaneous coating of the inside surface of each pipe. Useful in the application of corrosion protecting coatings to metal pipes for use in heat exchanger prodn. Coatings of refractory metals can be applied to the external surfaces of the pipes. The temp. of the diffusion coating process can be raised to step up the prodn. process as a whole. Coatings of different chemical compsn. can be coated simultaneously on the surfaces.