First, water side corrosion includes:
1. Dissolved Oxygen Corrosion: In the soda system, the most prone to metal corrosion is corrosion of the steel by dissolved oxygen in the water. Anti-corrosion method: Effectively remove oxygen from boiler water, increase the flow rate of water flow, avoid oxygen accumulation in individual areas, make oxygen and metal wall evenly contact, and form relatively uniform corrosion.
2. Free carbon dioxide corrosion: Hydrogen depolarization corrosion caused by acidic substances in water. Anti-corrosion method: remove CO2 and carbohydrates in boiler feed water as much as possible.
3. Corrosion under sediment: When the boiler is attached with scale or slag on the metal surface, severe corrosion will occur underneath it, called deposit corrosion. Anti-corrosion method: keep the pH value of the water in the boiler between 9 and 11. The protective film on the metal surface of the boiler is stable and corrosion will not occur.
4. Steam-water corrosion: It is a chemical corrosion caused by the oxidation of metallic iron by steam. Prevention method: Deterioration of the evaporation section with a small inclination angle to ensure normal water circulation. For superheaters with high overheating temperature, alloy steel pipes with good heat resistance and corrosion resistance should be used.
Second, smoke side corrosion
1. Gray matter corrosion: common corrosion forms of high temperature furnace tubes such as superheaters and reheaters. Prevention methods: control the furnace tube temperature, skip the melting point of the condensate, control the oxygen content in the delay, control the surface treatment of the furnace tube and control.
2. Dew point corrosion: The SO2 gas generated by combustion is combined with the comfortableness of the flue gas, and the generated sulfuric acid condenses and corrodes the metal on the surface of the metal below the dew point. Prevention method: Reduce the production of sulfur in combustion.
3. Stress corrosion: refers to the brittle cracking of the metal under the action of a specific corrosive medium and a certain horizontal tensile stress.
The boiler is in a very special operating environment. Temperature, pressure and corrosive media make it suitable for a variety of corrosion conditions. Only by fully understanding the causes of these corrosions can effective preventive measures be taken to prevent the boiler from being corroded.
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