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The term "carbon steel (PTFE) lining" often refers to a coating of polytetrafluoroethylene (PTFE) on the inside wall of carbon steel pipes. This lining combines the chemical inertness and non-viscosity of PTFE with the mechanical strength of carbon steel.
link:https://www.ttptfe.com/fluoroplastic-pipe/polytetrafluoroethylene-ptfe-lining/ptfe-lined-tubing.html
Ptfe Lined Tubing