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The integrity of flange connections is crucial for fluid transport pipeline systems. Whether it is pipeline systems for transporting chemical substances such as hydrocarbons or water supply pipelines, leaks at flange connections can have serious environmental and economic consequences, and may even pose significant safety risks. If the flange is not protected and is exposed to a corrosive environment or polluted industrial air, the corrosion rate will be very high. Furthermore, due to the complex geometry of flange connections, gap corrosion between the two flange surfaces as well as galvanic corrosion between different metals can easily occur, all of which can severely damage the integrity of the pipeline system. This article introduces several practical methods for addressing flange corrosion. To meet stringent production requirements and reduce sudden shutdowns caused by leaks, effective monitoring and detection are essential. Typically, technicians are more concerned about leakage issues between the flange surfaces and overlook the protection of the fasteners and the outside of the pipes, which can lead to extremely serious consequences in harsh external environments. Insufficient external protection accelerates and exacerbates the damage to the flanges and fasteners, leading to a rapid deterioration of the entire sealing system; this can quickly compromise the structural integrity of the system and result in seal failure. Since visual inspection of the sealing surfaces of flange connections can only be carried out when the entire system is shut down, the inspection procedure should be as simple as possible; therefore, external corrosion should be removed first. If it is not possible to shut down the machine, ultrasonic technology must be used for testing; when external corrosion cannot be controlled, this process becomes more complex and accurate test results cannot be obtained. Therefore, to monitor the entire system and provide effective quality control and maintenance procedures, external corrosion protection for flanges and fasteners is crucial. Existing solutions: An ideal solution should offer excellent corrosion protection along with simple installation procedures. It should also be suitable for flanges of various sizes and shapes, and allow for easy handling of the bolts during maintenance. Common solutions available on the market currently include: 1. Maintenance paint solutions. Maintenance paint is a hard coating that can be applied directly to the substrate; it is usually an epoxy or polyurethane-based coating. Flanges have many corners and edges, and due to the thinning effect at these edges, conventional painting systems find it difficult to cover them effectively. Although a thicker coating solves the problem of edge protection, it also seals off the fasteners, making it impossible to remove them during subsequent repairs. Furthermore, operating the bolts damages the coating, and repainting is necessary after maintenance. II. Mechanical solutions mainly involve sealing the gaps around flanges and the flange surfaces using guards and clamps, which are typically made of stainless steel or plastic and equipped with rubber seals. This protection method lacks flexibility, as it requires the use of covers or fixtures that are perfectly matched to flanges of various sizes. III. Tape or semi-solid anti-corrosion strip solutions: Tape in roll form (such as petrolatum tape, wax-based or elastic polymer bandages) provides protection by being wrapped around the surface of the substrate. Due to the good water resistance of semi-solid polymers, this protection method can provide reliable corrosion protection. However, if the flange has a complex shape, this material is not only time-consuming but also difficult to work with. When it is necessary to remove or install bolts, the material is relatively soft and easy to cut, but it is difficult to re-seal it and restore its original protection after removal or installation; usually, reconstruction is required. IV. Hot-melt plastic solutions Hot-melt plastics are essentially wax-like, meltable polymers that can be heated to high temperatures, and they are applied to the surface of substrates using specialized hot-melt equipment. The advantage of this protection method is that it can be remelted and reused, saving costs. However, this method also requires welding work, specialized equipment, and construction services; although it can be reused, it is difficult to open and seal during maintenance. V. Polymer seal bag solution: The seal bag can completely enclose the flange, and its composition includes a low-permeability polymer, corrosion-inhibiting vapor, and desiccant. It is easy to install, but the ends of the bag are sealed only with tape, rather than through a durable mechanical bond. There is a large amount of steam space inside the bag, which facilitates the accumulation of significant amounts of moisture; moreover, the corrosion inhibitor will also be depleted over time. Although the aforementioned solution can provide a certain degree of corrosion protection, it still has some shortcomings in terms of construction and maintenance; therefore, effective solutions need to be explored to offer long-term and comprehensive protection for flanges. VI. New type of peelable sealing film system: To address the issue of flange corrosion, some companies have utilized the chemical properties of polymers to develop a new type of peelable sealing film system that is both durable and sufficiently elastic. It can be peeled back forcefully without tearing, possesses the elasticity of rubber, and is completely free of isocyanates and toxic metal catalysts. This system is specifically designed to provide protection for flanges, fasteners, and related piping; it can be bonded to manually treated substrates without the need for welding, thereby making construction safer and simpler. This system uses a corrosion inhibitor as an undercoat to provide overall corrosion protection; meanwhile, the coating itself has strong adhesion properties, which allow all moisture within the system to be eliminated. ► Corrosion resistance of the system: The corrosion resistance of this system is evaluated through salt spray testing, which involves exposing the sample to a salt spray environment for an extended period in order to assess the corrosion resistance of the coating. The salt spray chamber converts a sodium chloride solution with a mass fraction of 5% into high-temperature salt spray at 35°C. The test sample is an assembled flange connection, with bare steel on one side and the sealing film system applied on the other side. The sample was exposed to a salt spray environment for 1000 hours, and no signs of corrosion were observed beneath the sealing film system. In contrast, the bare steel portion on the other side of the flange has suffered severe corrosion.