Steel Pipelines and Tubing Materials in Chemical Plant

Stainless steel has good properties of high temperature resistance, low temperature resistance and corrosion resistance of various media. It has been widely used in chemical equipment and is the preferred material for corrosion resistance. In some corrosive media, stainless steel corrosion resistance is much better than carbon steel, often take zero corrosion margin in the design. The service life of stainless steel can be several times or even dozens of times higher than carbon steel, so although the equipment one-time investment is high, it can save a lot of money in general. This is the reason why stainless steel material plays a very important role in chemical production. However, this kind of high quality material is not reasonable, will also cause a lot of waste, should cause high attention.

(1) the influence of chloride ion on the corrosion resistance of stainless steel equipment, the content of chloride ion in the working medium and the working temperature have a great influence on the stress corrosion of stainless steel.

For example, the water heater in a factory in Tianjin was seriously corroded. After using all stainless steel material, the phenomenon of leakage appeared in a few months. After careful analysis, the hot water was found to contain gas ions and oxygen. Stainless steel can not withstand chloride ion corrosion at a certain temperature, especially in the presence of oxygen in the medium, the presence of oxygen can accelerate the corrosion. The corrosion resistance of stainless steel is not as good as that of carbon steel at a certain concentration and temperature of chloride ion. However, under the condition of little or high content of atmosphere ions and low temperature, it is far better than carbon steel. 

At this point, temperature has a greater effect on corrosion resistance than chloride ion concentration. When choosing material so, outside dividing the concentration that considers atmosphere ion, should notice the effect of temperature especially. Increasing the content of brocade in austenitic alloy is an effective method to prevent stress cracking caused by atmosphere ions. The alloy containing more than 42% of gold can fully withstand the corrosion cracking caused by atmosphere ions, such as 825 alloy, G alloy, 625 alloy. The alloys containing 8%~12% nickel are most prone to stress cracking.

(2) dew point on the corrosion resistance of stainless steel equipment corrosion is often intensified with the rise of temperature, but the degree of dew point corrosion is not only related to temperature, and the dew point temperature of the working medium is more closely related. Dew point corrosion on stainless steel is also greater. For example, the corrosion of the equipment is greatly improved by adjusting the inlet and outlet temperatures of hot water and avoiding the dew point temperature.