Corrosion prevention methods for heat exchangers

Thread Content

Heat exchangers are important equipment in chemical production, accounting for 40% of the total weight of process equipment. 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 diffusion coating, aluminum-silicon diffusion coating, and aluminum-chromium-silicon diffusion coating, 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 prone to deformation. The layer formed through this process is uniform and does not tend to flake off. Acting as an anodic protection layer, the zinc infiltration layer provides better protection and can significantly extend the service life of the equipment.