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How does a plate heat exchanger prevent medium corrosion?

Release time:

2025-04-25

Plate heat exchangers prevent medium corrosion mainly through material selection, structural design, process control and auxiliary protection measures. The following are specific methods:

1. Material selection

(1).Corrosion-resistant metal materials

a). Select stainless steel (such as 316L resistant to chloride ion corrosion), titanium (resistant to seawater and chloride ions), Hastelloy (resistant to strong acid), nickel alloy, etc. according to the characteristics of the medium.

b). For example: titanium is suitable for chlorine-containing media, and 254 SMO stainless steel is resistant to high-concentration salt water.

(2).Non-metallic materials: Graphite plates, polytetrafluoroethylene (PTFE) linings or all-plastic heat exchangers are used in extreme environments such as strong acids and alkalis.

2. Structural design optimization

(1).Avoid galvanic corrosion: Use insulating gaskets (such as PTFE) to isolate different metals when they come into contact to prevent electrochemical corrosion.

(2).Reduce dead corners and gaps: Optimize the flow channel design to avoid medium retention and reduce the risk of crevice corrosion.

(3).Uniform velocity distribution: Design reasonable flow channel width and diversion area to prevent local velocity from being too high (erosion) or too low (deposition corrosion).

3. Process control

(1).Medium treatment

a).Adjust pH value: Add corrosion inhibitors (such as phosphates and chromates) to neutralize acidic or alkaline media.

b).Deoxidation treatment: Remove dissolved oxygen (especially for high-temperature water media) to reduce oxidation corrosion.

c).Filter impurities: Prevent solid particles from eroding or depositing to cause local corrosion.

(2).Temperature and pressure control: Avoid overheating (such as stainless steel is prone to intergranular corrosion at high temperatures) or pressure fluctuations that cause material fatigue.

4. Surface treatment technology

(1).Anti-corrosion coating: Coatings such as epoxy resin and PTFE on the surface of the plate to isolate the corrosive medium.

(2).Passivation treatment: Stainless steel plates are passivated with nitric acid to form a dense oxide film (Cr₂O₃) to improve corrosion resistance.

(3).Electrochemical protection: Cathodic protection (such as sacrificial anode) is used in electrolyte environments such as seawater.

5. Maintenance and monitoring

(1).Regular cleaning: Remove scale and sediment (chemical cleaning or mechanical cleaning) to prevent under-scale corrosion.

(2).Leak detection: Monitor the status of the sealing gasket to prevent corrosion caused by media leakage or cross-contamination.

(3).Corrosion monitoring: Install corrosion coupons or online sensors to evaluate the material corrosion rate in real time.

6. Response to special working conditions

(1).High-chlorine environment: Use titanium or super austenitic stainless steel to avoid chloride ion stress corrosion cracking (CLSCC).

(2).Acidic medium: Use Hastelloy C-276 or plastic-lined design.

(3).Microbial corrosion: Add bactericides (such as sodium hypochlorite) or use antibacterial coatings.

7.Summary

Preventing corrosion of plate heat exchangers requires a comprehensive design based on media characteristics (composition, concentration, temperature), material compatibility and operating environment. Through material selection, process optimization and proactive maintenance, the equipment life can be significantly extended and the risk of corrosion can be reduced. For harsh working conditions, it is recommended to consult a professional anti-corrosion engineer for customized solution design.

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