No matter it is chain grate boiler or the fuel gas boiler ,they are all trend to be erode. The following is some reasons and actions.
Caused by water/liquid
The dissolved oxygen corrosion: in soda system, the steel is prone to be corroded by dissolved oxygen in water. Anticorrosion methods: get rid of oxygen in boiler water,and improve the flow velocity. To avoid the accumulation of oxygen in individual area, we should make it contacts with the metal surface evenly to form a uniform corrosion.
Free co2 corrosion: depolarization corrosion caused by the acidic hydrogen Anti-corrosion in the water . methods: to remove CO2 and carbohydrates in boiler feed water.
Sediment corrosion: when scale or water slag adhered on the surface of the metal, the severe corrosion occurs, known as the sediment corrosion. Anti-corrosion methods: keep the pH of the water in the boiler between 9 to 11, then the boiler protective film on the surface of the metal will stable, corrosion will not happen.
Caused by flue gas
Gray matter corrosion: this is common corrosion form for high temperature furnace tube such as the superheater and reheater . Prevent method: tackle from the control of furnace temperature, skip melting point of the condensation, control and delay the oxygen content in furnace ,and pay more attention to the tube surface treatment and select.
The dew point corrosion:SO2 generated by burning gas, combined with oxygen in flue gas, and became the sulfuric acid, condensed on the surface of the metal that is below the dew point and corroded of metal. Prevent methods: reduce burning sulfur.
Stress corrosion: refers to the action of brittle cracking of the metal in a specific corrosive medium and a certain level of tensile stress at the same time.
Industrial boiler is in a very special operating environment, because corrosive mediums such as temperature, pressure have produced a variety of corrosion conditions. only fully understand the reasons of the corrosion and take effective measures, can we protect boiler from corrosion damage.
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