a method of powder coating the inside of tubular goods , such as oil field pipe and the like , by connecting one end of the pipe to a means for producing a flow of compressible gases therethrough . the other end of the pipe is open to atmospheric pressure . a valve means is connected upstream of the pipe between the inlet end thereof and a container for holding a single charge of plastic powder . the charge of powdered plastic is isolated upstream of the pipe inlet . the charge is of sufficient size to coat the entire inside peripheral wall surface of the pipe with a substantial uniform coating of plastic . the pipe is heated above the softening temperature of the plastic and rotated so that when the valve is opened air flows through the pipe and establishes a pressure gradient across the entire length of the pipe to cause the captured charge of plastic to form a pocket of dispersed plastic particles which is forced through the pipe by the air flow , causing plastic particles to be deposited and fused to the hot rotating inner surface of the pipe .