3PE-coated steel pipe for wastewater treatment

3PE‑coated steel pipe: The 3PE coating is ideally suited for protecting pipelines in complex terrains and under severe corrosion conditions. In oilfield construction, 3PE‑coated pipes have come to dominate domestic applications in oil, water, and gas transmission projects, thanks to their outstanding chemical resistance, superior mechanical protection, and long service life. These products are widely used in pipeline systems across industries such as petroleum, natural gas, chemicals, power generation, defense, shipbuilding, papermaking, heating, water supply and drainage, hydropower stations, piling, bridge construction, and steel structures, earning consistent acclaim from a broad base of users.

Before applying anti-corrosion treatment, the base material of 3PE‑coated steel pipes—used for cable protection in power, telecommunications, and highway applications—must undergo inspection and documentation upon entry to the pipe‑handling platform. The outer surface is then blast‑cleaned to remove rust, followed by verification of surface cleanliness and anchor profile depth to ensure compliance with specifications. Non‑conforming sections are manually ground with an abrasive wheel until they meet the required standards. Tape is wrapped around the pipe ends, dust is removed, the pipe is heated to the specified temperature using medium‑frequency induction, epoxy powder is applied by spraying, adhesive is extruded and wrapped on one side, and PE is extruded and fused on the other. The coated pipe is then water‑cooled, and qualified products are marked before being transferred to the unloading platform and stacked for shipment. To prevent explosions, personal injury, and property damage when transporting flammable or toxic fluids, spiral‑welded steel pipe manufacturers adhere to appropriate process standards, continuously meeting critical performance requirements and ensuring quality and safety throughout testing and measurement for market use. Among internal lining corrosion‑protection methods, cement‑mortar lining is widely employed due to its low cost; this approach leverages a cement‑mortar protective layer that integrates three materials into a single unit, firmly bonding with the steel pipe to form an excellent corrosion‑resistant coating.

At present, the performance of anti-corrosion coatings both domestically and internationally has been highly satisfactory, with very few reports of defects arising during service. Corrosion‑testing environments typically include soil and water; the primary focus is on assessing stress corrosion cracking. In such tests, steel pipes with defective polyethylene coatings are subjected to corrosive conditions combined with applied stresses. The test medium consists of sand containing NaHCO3, at a temperature of 70°C, with a pipe‑to‑soil potential ranging from −430 to −460 mV. The pipe surfaces undergo various pre‑treatments, and all specimens are tested under pressurized cyclic loading. The appropriate coating grade should be selected based on the customer’s specific requirements: for standard external protection of casing pipes, the ordinary grade is generally sufficient; however, for direct fluid service—such as acids, alkalis, or natural gas—it is advisable to use the enhanced grade. The specific manufacturing process for three‑layer PE polyethylene spiral‑wrapped insulated pipes is as follows: the spiral pipe is heated by medium‑frequency induction, followed by shot blasting for rust removal and quality inspection; subsequent medium‑frequency heating, application of epoxy powder, coating with an adhesive, outer extrusion of polyethylene, water‑cooling, leak testing of the coating, and finally stacking of the coated pipes. In general, anti‑corrosion and insulation technology for spiral pipelines involves applying an external protective coating to the pipe’s outer surface to mitigate corrosion and extend its service life, making it suitable for wastewater treatment discharge lines, sewage pipes, and anti‑corrosion projects in biological tanks.