Why is 304 Stainless Steel not Suitable for use as a Material for Flue Gas Desulfurization Devices?
- KEPLER TEAM
- Jan 10, 2022
- 2 min read
The stainless steel plate obtains the ability to resist corrosion and rust by the continuous penetration and oxidation of a very thin, firm and fine layer formed on its surface. However, if for some reason, the passive film on the surface of the stainless steel plate is continuously damaged, the air or liquid in the surrounding medium will continue to infiltrate or the iron atoms in the metal will continue to separate out, forming loose oxidative corrosion.
A stainless steel sheet can have good corrosion resistance in many media, but in another medium, it may corrode due to low chemical stability. Therefore, it is impossible for a stainless steel to be corrosion resistant to all media. The corrosion of stainless steel plates can be divided into physical corrosion, chemical corrosion and electrochemical corrosion according to the mechanism. Most of the metal corrosion in engineering practice is electrochemical corrosion. The main corrosion forms of stainless steel are uniform corrosion (surface corrosion), pitting corrosion, crevice corrosion and stress corrosion.
Petrochemical plants, coal-fired power plants, iron and steel smelters, etc. produce a large amount of flue gas every year, which contains a large amount of acid gases, such as SO, HCl, etc. Since the 1980s, Europe has rigidly stipulated that combustion power plants should use flue gas desulfurization devices (FGD). China started the thermal power desulfurization project at the end of the 20th century. The 10-20 years at the beginning of this century were the key period for the desulfurization of China thermal power plants.
In the flue gas desulfurization process, the temperature of the flue gas mixture is lower than its dew point temperature, which causes H2SO4 and HCl in the wet flue gas to condense in the pipeline and desulfurization device, causing serious corrosion (pitting corrosion is more common).
In the desulfurization simulation solution, temperature is the main factor affecting the corrosion of 304 stainless steel: at normal temperature, 304 stainless steel has good corrosion resistance in dead green solution, but it is easy to produce pitting corrosion when it is heated to 40 °C, and at 60 °C Comprehensive corrosion, the surface has been pitted, so 304 stainless steel is not suitable for use as a material for flue gas desulfurization devices. In terms of temperature and time, 2205 duplex stainless steel has good corrosion resistance and is suitable for use as a material for flue gas desulfurization devices.
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