Case studies on anti-corrosion and rust protection for condenser tube sheets and water chambers (multiple images)

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【Abstract】Based on the corrosion mechanisms of the condenser tube sheet and water chamber, the use of polymer composite materials as anti-corrosion and rust-proof coatings is proposed； An analysis was conducted on the common corrosion problems in condensers ； An analysis and explanation are provided regarding the use of 128L self-leveling polymer-ceramic composite materials for the protection against corrosion and rust on condenser tube sheets. 【Keywords】Waste heat power generation, condenser, c, anti-corrosion protection, polymer composite materials. I. Equipment overview: Condensers are primarily used in turbine power systems and are divided into water-cooled condensers and air-cooled condensers. In addition to condensing the turbine exhaust steam into water for reuse in the boiler, the condenser can also create and maintain a vacuum at the turbine exhaust site. Water-cooled surface condensers are divided into single-pass and double-pass types based on the flow pattern of the cooling water. A water-cooled condenser is mainly composed of a shell, tube bundle, hot well, water chamber, and other components. The exhaust steam from the turbine enters the casing through the throat, condenses into water on the cooling tube bank, collects in the hot well, and is pumped out by a condensate pump. Cooling water (also known as circulating water) enters the cooling tube bundle from the inlet water chamber and exits from the outlet water chamber. To maintain a high vacuum and excellent heat transfer efficiency in the condenser during steam condensation, exhaust equipment is also provided; it continuously removes air and other non-condensable gases that leak into the condenser. Pumping equipment mainly includes water jet pumps, steam jet pumps, mechanical vacuum pumps, and combined vacuum pumps. II. Analysis of corrosion causes The materials used for the water chamber and tube sheet of the condenser are ordinary carbon steel plates, which consist of ferrite and a small amount of cementite. The circulating water they come into contact with has not been thoroughly treated and contains various electrolytes. Since the electrode potential of ferrite is lower than that of cementite, it acts as the anode, while cementite becomes the cathode; these two poles together form numerous corrosion cells. When the circulating water is seawater or water that has not been properly treated, it further accelerates the electrochemical corrosion of the tube sheet and water chambers, resulting in rust of different forms and compositions. In severe cases, this can even lead to perforations in the tube sheet and water chambers, causing coolant leakage and contamination of the condensate water. Therefore, it is essential to apply anti-corrosion treatments to the tube sheets and water chambers of condensers. III. Analysis of the Advantages in the Technical Applications of Polymer Composite Materials. Polymer composite materials are a high-tech field that has developed on the basis of disciplines such as polymer chemistry, organic chemistry, colloid chemistry, and material mechanics. By utilizing polymer penetration to create forces between molecules, van der Waals forces and hydrogen bonds are formed between these materials and the components being repaired, thereby ensuring good adhesion between them and the components under repair. The special molecular structure of polymer composite materials endows them with properties such as the ability to adapt to alternating deformations and temperature changes, ensuring that these materials possess excellent corrosion resistance, cavitation resistance, and wear resistance. Its high-density molecular weight and smooth surface coating can improve the efficiency of vacuum pumps. Polymer composites are non-volatile, non-toxic, and harmless, and can come into direct contact with the skin. Using polymer composite repair materials to apply organic surface coatings for corrosion protection is one of the effective anti-corrosion measures currently in use. Polymer composite materials can form a cured protective coating on the substrate to be protected, serving as a barrier that separates the base steel plate from circulating water, thereby preventing corrosion ； The coating’s resistance to penetration, stability against corrosive agents, strong adhesion, and appropriate mechanical properties ensure the effectiveness of the protective coating as well as the operational lifespan of the equipment. IV. Equipment and tools for polymer application processes: power supply, sandblasting equipment, axial flow exhaust fans, canvas or plastic sheeting, rubber stoppers, anhydrous ethanol, scrapers, brushes, lighting fixtures, rubber gloves, safety helmets, protective glasses, dust protection gear, cleaning cloths, garbage bags, etc. 1. Preliminary preparation: Use a hair dryer and blower to dry the water on the surface and inside of the pipe, then plug the pipe end with a rubber stopper and cover the flange to ensure that the pipe end is not damaged during sandblasting (see figure on the right) ； 2. Sandblasting treatment: During sandblasting, the equipment should be enclosed with canvas (plastic sheeting), and axial flow exhaust fans as well as air ducts should be installed to prevent the sand particles and dust generated during sandblasting from contaminating the environment and surrounding equipment. Sandblasting can use quartz sand, which removes the surface oxide layer and creates a surface roughness of 4 mils. To achieve the natural color of the base metal ； 3. Solution cleaning: Use anhydrous ethanol (analytical grade) to clean away the impurities from the metal surface after sandblasting ； 4. Apply the repair and protective material: Mix the product strictly according to the proportions. First, the pitted areas on the inner wall of the condenser tube sheet are repaired using 2296 polymer nanocomposite functional material until a satisfactory flat surface is achieved. Then, 128L of self-leveling polymer-ceramic composite material is applied evenly to the surface of the tube sheet using tools such as scrapers and brushes, ensuring that there are no missed areas, sagging, pinholes, or bubbles on the coated surface; special attention is paid to the joints between the panels and the tubes in order to achieve a leak-proof seal ； 5. Curing and trimming: After 8 to 12 hours of curing, gently tap the rubber plug with a rubber mallet to loosen it and remove it, then trim any remaining material at the tube opening. If there is a defective area, a second repair can be performed. Application of image information: 5. Conclusion The excellent anti-corrosion properties of polymer composite coatings are effectively utilized in the protection of condenser tube sheets and water chambers against corrosion. These coatings can be used not only for preventing corrosion in already operational condensers in power plants, but also for protecting newly manufactured condensers from corrosion. Numerous engineering applications have proven its stable and reliable performance; it effectively reduces or eliminates corrosion that occurs during the operation of condensers, thereby extending the overall service life of the equipment. It has become an essential technical tool in the equipment management practices of many corporate users.