Polytetrafluoroethylene (PTFE, code F4) sheathed corrosion-resistant thermocouples and resistance temperature detectors (RTDs) are designed for temperature measurement in corrosive chemical and heat-treatment processes, where conventional stainless steel sensors fail within days to weeks.
In chemical reaction systems and mechanical heat-treatment lines, such as electroplating, pickling, and oxidation, process fluids almost always contain strong acids or strong bases. Temperature control in these processes is critical, but standard sensors with stainless steel outer sheaths cannot meet the corrosion-resistance requirements and often fail within one month or even within a few days. This new product line solves this failure mode by isolating the metal sheath and sensing element from the measured medium.
These sensors utilize the excellent chemical stability of PTFE. F4 is widely known as the "King of Plastics" and can withstand strong acids, including aqua regia, sulfuric acid, hydrofluoric acid, concentrated phosphoric acid, and nitric acid; strong bases, such as boiling sodium hydroxide solution; and strong oxidizing agents, reducing agents, and organic solvents. It also offers aging resistance, radiation resistance, flame retardancy, non-stick properties, and a low coefficient of friction, making it one of the most corrosion-resistant materials available.
The construction employs a multilayer sealing design: F4 lead wires, sealant, F4 outer sleeve, stainless steel tube, magnesium oxide powder insulation, and sensing element. PTFE is sintered onto the surface of the thermocouple or RTD sheath through a specialized molding and sealing process. For longer or narrower sheaths-including those with diameters of less than 10 mm-a reliable tube-sleeving and end-sealing method is used to completely isolate the metal sheath from the process medium. The F4 version has a continuous operating temperature range of -180 °C to 250 °C, and an F46 (fluorinated ethylene propylene, FEP) version is available for use up to 200 °C. Field service life exceeds one year.
These sensors are suitable for fluorochemical, sulfur chemical, chlor-alkali, pharmaceutical, and mechanical heat-treatment applications. They are installed on corrosive liquid tanks, vessels, and pipelines to monitor process temperature directly at locations where metal sensors previously could not survive.
For purchasing and engineering procurement teams evaluating corrosion-resistant temperature sensors, this series offers configurations tailored to each measured medium and installation condition. Detailed specifications and application-specific consultations are available upon request.