Introduce several methods for preventing corrosion in heat exchangers
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Heat exchangers are important equipment in chemical production, accounting for 40% of the total weight of process equipment. The petrochemical industry needs to replace over 5,000 heat exchange units each year, which consumes 26,000 tons of steel and results in direct losses of over 500 million yuan. Corrosion prevention methods: 1. Corrosion-resistant materials: Use corrosion-resistant materials such as stainless steel, titanium, and aluminum brass. 2. Electrochemical protection: Carbon steel heat exchangers are inexpensive but have poor corrosion resistance. For large heat exchangers, external current cathodic protection is generally used, while for smaller ones, sacrificial anode cathodic protection is more common; these methods can help reduce the corrosion of heat exchangers. 3. Ni-P electroless plating, coating: The heat exchanger is subjected to overall electroless plating to form a nickel-phosphorus coating, which acts as a cathodic coating and helps to mechanically isolate corrosive agents. The coating provides limited protection and is prone to peeling during maintenance. 4. Aluminum infiltration: Infiltrating aluminum elements into the working surface layer, using methods such as the powder method, gas phase method, and slurry method, can enhance the resistance of steels, non-ferrous metals, and alloys to high-temperature oxidation and gas corrosion; they also exhibit good corrosion resistance in environments exposed to air, H2S, CO2, and seawater. Aluminum-chromium carburizing, aluminum-silicon carburizing, and aluminum-chromium-silicon carburizing, all based on aluminization, are widely used. 5. Zinc coating: It is one of the most economical and common corrosion prevention methods. The zinc infiltration process operates at a relatively low temperature, around 400–500°C; as a result, the heat exchanger is less likely to deform. The layer formed through this process is uniform and does not tend to flake off. Acting as an anodic protective layer, the zinc infiltration layer provides better protection and can significantly extend the service life of the equipment.
In the chemical industry, the main corrosion prevention measures for heat exchangers include the following: 1. Using corrosion-resistant materials: such as stainless steel, titanium, and aluminum brass, which possess excellent corrosion resistance. 2. Electrochemical protection: For heat exchangers made of carbon steel, corrosion can be slowed down through cathodic protection using an external current or by employing sacrificial anodes. 3. Ni-P electroless plating and coatings: By applying Ni-P electroless plating to the surface of heat exchangers, a nickel-phosphorus coating is formed that can isolate corrosive agents. At the same time, using paint can also provide some protection, although there may be issues with peeling. 4. Aluminum infiltration treatment: This process involves infiltrating aluminum into the surface of the heat exchanger, thereby enhancing its resistance to high-temperature oxidation and corrosion; it is suitable for use in various environments with corrosive agents. 5. Zinc infiltration coating: By forming a zinc infiltration layer on the surface of the heat exchanger, effective anodic protection is provided, which extends the service life of the equipment. Moreover, the equipment does not tend to deform during the treatment process, and the coating is uniform and resistant to peeling. .