What is the corrosion prevention effect of equipment lined with PTFE? Which anti-corrosion process will prevail as the industry develops?

Plate lining anti-corrosion process: The plate lining process is widely used internationally and has also been adopted by some users in China. The lining materials and auxiliary materials used in this process are all supplied by specialized foreign manufacturers. It features advanced technology and reliable quality, enabling it to address the three key challenges in the chemical industry – cleanliness, temperature control, and corrosion resistance. Moreover, it is not restricted by manufacturing equipment. In polysilicon and propylene oxide projects, large storage tanks with a diameter of 5 meters and a length of over 15 meters have been successfully manufactured using this fluorinated lining anti-corrosion method, which has received high praise from users. The fluoroplastic sheets used include TFE, PVDF, PFA, MF, ECTFE, and FEP; their raw materials are produced by renowned foreign fluoroplastic companies, while the sheets themselves are manufactured by well-known foreign industrial plastic manufacturers as well as Swiss engineering plastic companies. Roll-coating anti-corrosion process: The roll-coating process is widely used both domestically and internationally. It is not affected by the shape of the equipment or its complex structure, and it enables seamless and flawless forming in a single step. The materials to be used can be determined based on the temperature of the medium and the operating conditions. At present, the roll-coating equipment available with our company can be used to produce anti-corrosion equipment and pipe components up to 3.3 meters in length. Our company’s plastic-lined equipment utilizes advanced heat-rotation technology and imported high-performance materials. Depending on the specific requirements of each user, we select appropriate formulations and the optimal lining thickness to achieve a thermal fusion bond between the plastic and the steel substrate. Its features include the integration of steel and plastic, resulting in strong bonding; it can expand and contract simultaneously, making delamination unlikely. The lining layer has no overlapping seams, no bubbles or pinholes, offers high impact resistance and good impermeability, has a smooth and shiny surface similar to that of enamel, has a low friction coefficient, and is resistant to scaling. Any structural-shaped equipment, pipes, and pipe fittings can be processed. The plastics mainly used at present are ETFE (F-40) and P0. 　　It is copolymerized from 1:1 ratios of tetrafluoroethylene and ethylene. ETFE (F-40) fluoroplastic is derived from DuPont in the United States and Asahi Glass in Japan, and is primarily used for corrosion-resistant linings. This material possesses the corrosion resistance of polytetrafluoroethylene, along with a strong adhesive property specific to metals, overcoming the issue of polytetrafluoroethylene’s inability to bond to metals. Additionally, its relatively low coefficient of linear expansion is similar to that of carbon steel, which makes ETFE (F-40) an ideal composite material for use with metals. It also exhibits excellent resistance to negative pressures. Spray coating anti-corrosion process: This spraying process is widely used in the chemical industry, pulp and paper industry, food industry, and semiconductor industry. Our company has developed a range of products, including electrostatic spray-coated fluoropolymer coatings, PTFE (polytetrafluoroethylene, F2) equipment, and FEP (perfluoroethylene propylene, F46) products. Fluorinated pipe fittings, TFE-lined straight pipes and pipe fittings, are commonly known as loosely lined pipes. This process uses films turned from PTFE rods, which are then wound and sintered into shape. Suitable for conveying pipelines under normal or positive pressure (such as waste treatment pipelines), but not suitable for pipelines under load (such as at pump inlets and outlets, or pipelines where negative pressure can be generated due to height differences or sudden cooling). Pipe diameter range: DN25~1000mm. Operating temperature: -40~+230°C. Operating pressure: 1.6MPa. PTFE-lined straight pipes and pipe fittings. Manufacturing process: Several layers of PTFE film are first wrapped around a mold, followed by the spiral winding of steel wire (φ0.5-1mm) around the PTFE film; several more layers of PTFE film are then wrapped around the steel wire, and finally the assembly is sintered in a furnace to take its final shape. PTFE-lined pipes manufactured using this process have a smooth inner wall, while the outer wall develops spiral corrugations due to the volume of the steel wires and their elastic force. Insert it into the steel pipe, and fill the space between the outer wall of the PTFE-lined tube and the inner wall of the steel pipe with filling resin (to remove any residual air). This filling resin can bond tightly to the steel pipe. At the same time, it can tightly wrap around the outer wall of the spiral PTFE lining; once the resin cures, spiral ridges are formed that interlock with the ridges on the outer wall of the lining. This structure is similar to the combination of a nut and a bolt. On the one hand, it can effectively restrict and compensate for the thermal expansion and contraction of the PTFE lining ； On the other hand, the use of steel wire significantly improves the ability of the PTFE lining to withstand negative pressure. Port size: DN25~200mm. Operating temperature: -50~+230°C. Operating pressure: 0.5~1.6 MPa. It consists of PTFE-lined straight tubes formed by pushing (extruding) pipes. Manufacturing process: First, imported PTFE, PFA, FEP, or PVDF powders are used to create pipes through pushing (extruding), and then these pipes are forced into seamless steel tubes (the outer diameter of the lining tube is 1.5–2 mm larger than the inner diameter of the steel tube), thereby achieving a gap-free lining. To eliminate stress, it is placed in a furnace and heated to 230°C for a constant-temperature treatment, so that it can be used at temperatures below 230°C. At the same time, the axial tensile strength of pushed (compressed) pipes is significantly better than that of wound pipes. This pipeline has ideal resistance to both positive and negative pressures. Port size: DN25~300mm. Operating temperature: -100~+230°C. Operating pressure: -0.09~1.6 Mpa. The pipe fittings are made from fluoroplastics such as PFA, FEP, PVDF, and PTFE, and are formed through molding; the lining thickness is 3–7 mm, granting them good resistance to both positive and negative pressures. Pipe diameter range: DN25~500mm. Operating pressure: -0.09~+1.6 MPa. Operating temperature: -100~+230°C (PFA), -100~+200°C (FEP), -100~+200°C (PVDF). At present, the maximum diameter of domestically produced PTFE pipes produced by push/pull methods is 300 mm, while the optimal diameter for PTFE-lined pipes with steel wire wrapping is only 200 mm. To address the issues of resistance to positive and negative pressures in DN25-500mm lined straight pipes and pipe fittings, we employ the following lining process ； Inside the PTFE loose liner, metal support rings coated with PTFE (6–16 mm in diameter) are placed at regular intervals; the inner wall of these rings is corrugated, which serves to secure the support rings ； On the other hand, it provides better compensation for the thermal expansion and contraction of the PTFE lining, enabling the pipeline to have good resistance to both positive and negative pressures. Standard diameter range: DN25~500mm. Operating temperature: -100~+230°C. Operating pressure: -0.09~+1.6MPa. Source: 51 Pressure Vessel Forum http://bbs.51cysb.com. Original link: http://bbs.51cysb.com/thread-51223-1-1.html