Abstract: An in-line, continuous, roll-forming tube mill production line. The line includes a supply station for continuously supplying steel strip, a roll-forming station for forming the strip into a tubular configuration, and a welding station for joining by welding the edges of the strip. The line also has at least one station for performing a process which calls for the application of a liquid to the exterior of the tubing such as cleaning, rinsing or applying a coating. A preheating station is provided for preheating of the tubing by induction and a powder coating station applies a plastic coating or a metallically pigmented plastic coating to the exterior of the tubing, the powder coating station having a chamber and means for selectively isolating the tubing from chamber. Finally, the tube mill production line includes a heating station for baking and/or curing of the powder coating.