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Recently, influenced by the \"Opinions on Promoting Ultra-Low Emission Measures in the Steel Industry\" issued jointly by five ministries and commissions including the Ministry of Ecology and Environment, the projects aimed at achieving ultra-low emissions in existing steel plants have accelerated. During the transformation process of these steel plants, pipeline corrosion has become an increasingly prominent issue, and our company has received numerous inquiries in recent days regarding measures to prevent pipeline corrosion and leakage. This article, drawing on field protection cases of flue gas leakage in steel plants and corrosion-induced leakage in slag removal pipelines, details the causes of pipeline corrosion and leakage as well as precautions for online repair, for reference and discussion. I. Causes of pipeline corrosion and leakage: During the manufacturing process, pipelines often develop various defects due to issues such as manufacturing precision or process control, including pores, sand inclusions, and hidden cracks. Such defects are difficult to detect with the naked eye; they are usually discovered during pressure testing at the later stages of production, by which time most of the manufacturing processes have already been completed, resulting in significant production costs. At the same time, pipelines are also affected by various environmental factors during use, including material properties, medium corrosion, temperature and pressure, etc. These factors can cause sand holes, cracks, and leaks in the pipelines, and even lead to a reduction in the wall thickness of the material, thereby affecting the proper operation of the equipment. II. Several methods for protecting pipes from corrosion 1. Traditional repair techniques: To address pipeline leakage issues, traditional repair methods often involve stopping the operation, releasing pressure, and then carrying out welding repairs or using clamping devices to fix the problem. However, due to factors such as pipe wall thickness, material composition, and the type of fluid flowing through the pipe, welding repairs have significant limitations, and clamping devices are not suitable for pipes with complex structures. 2. Polymer composite repair process: For repairs using polymer composites, different repair methods are employed depending on the type of medium, temperature, pressure, and the extent of the leakage. Taking advantage of the materials’ excellent compressive and corrosion-resistant properties, the leaking areas can be repaired on-site. This approach ensures good repair results; generally, there is no need to shut down the pipeline and release pressure, and the repair process is quick and easy to carry out. The main advantages of polymer materials for the anti-corrosion protection of pipelines are: operation at room temperature on-site, simplicity in use, quick results with high efficiency. Moreover, their anti-corrosion properties are superior to those of metal materials, allowing them to effectively address leaks and provide anti-corrosion protection for metals; they can even serve to reinforce the structures to some extent. Their overall cost-performance ratio is excellent. The materials used in this article are Fosil Blue EE-101 and 2211F series. III. Application examples of on-site protection against pipeline corrosion in the steel industry 1. Leakage at the joints at the edges of flue ducts in steel plants. Equipment name: Flue ducts; Medium: Slightly acidic water vapor; Wall thickness: 1.8 mm; Temperature: 50–60°C; Material: Aluminum alloy; Gap width: Varies from 2 to 10 mm; Total length: 648 meters. The flue ducts in this enterprise suffered from joint problems at the edges due to issues during installation. Welding would cause further damage to the equipment, but using Fosil Blue polymer composite EE-101 together with glass fiber cloth can effectively resolve these problems. Repair steps: 1) Use tools such as a grinder or sanding belt to treat the surface of the gap, making it rough. 2) Wipe the leaking area with 99.7% anhydrous ethanol to ensure the surface is clean, dry, and firm. 3) Mix an appropriate amount of EE-101 anti-corrosion material (or 418 material) in the specified ratio until the color is uniform with no color differences, and apply it to the gaps using glass fiber cloth. 4) Once the material has cured, it will achieve anti-corrosion effects. 2. Equipment for enhancing corrosion protection of welds in slag-flushing steam pipelines: Slag-flushing steam pipeline; damaged areas: the pipeline and its welds; form of damage: corrosion; operating temperature: 60–80°C; medium inside the pipeline: slag-flushing steam; pipeline diameter: φ1300 mm; length to be repaired: 100 m. Depending on the material used, there are mainly two solutions to this problem: Photocurable materials. Procedure: 1) Grind the pipeline to make its surface rough and sturdy; grinding can be carried out in sections ； 2) Measure the dimensions of the polished surface, and cut the sheet material according to those dimensions ； 3) Cut the sheet material; avoid exposure to light while the sheet is open, and wrap it immediately with black oilcloth once cutting is complete ； 4) Clean the surface with alcohol, wait for it to dry, then apply the primer ； 5) Attach the sheet material: hold one end of the sheet with one hand while using the other hand to smooth it out in order to minimize wrinkles and bubbles; it is possible to apply the primer while attaching the sheet ； 6) Once pasting is complete, use a roller to flatten it. Be careful not to apply too much force while pressing the primer and sheet materials together, as this could result in uneven thickness; gently remove any bubbles to achieve a smooth surface ； 7) Wait for the material to cure ； 8) After curing, remove the surface film, clean the surface, and apply the topcoat material. Steps for winding polymer composite materials: 1) Carry out the preparatory work before construction, such as tools, materials, and other items. It mainly includes: brushes, anhydrous ethanol, 60-mesh sandpaper, scissors, putty knives, plywood, clean cotton cloth, etc ； 2) During repairs, take proper safety measures for personnel, clean up the construction area to prevent accidents ； 3) Use a grinder together with gears or sandpaper to grind the pipeline and its surrounding area, removing surface rust to reveal the original color of the metal ； 4) Thoroughly clean and wipe the area to be repaired with anhydrous ethanol or alcohol to ensure a clean and smooth surface ； 5) Mix Fushilan polymer composite 418 in proportion ； 6) Apply the polymer composite material 418, ensuring a thorough and even coating ； 7) Soak the glass fiber cloth thoroughly in the material and wrap it around the pipe, tightening it securely (pay attention to the curing time of the material to prevent premature curing due to the pipe’s temperature) ； 8) Use 418 material for surface coating to fully cover the glass fiber cloth ； 9) Repair completed; waiting for the material to cure. In addition to the two cases mentioned above, our company has further applications in the comprehensive reinforcement of pipeline corrosion: attached are the technical data for the polymer composite EE-101