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Do you know how spot corrosion is formed?


Due to the defects, impurities and solute in the steel, […]

Due to the defects, impurities and solute in the steel, the passivation film on the surface of stainless steel is relatively fragile in these places. When the etch pit exceeds the critical size, it is easily destroyed in the corrosive solution containing chlorine. It becomes the activated anode, and the surrounding area is the cathode area. The area of ​​the anode is very small. The current density of the anode is very large, and the active dissolution is accelerated, which then becomes many needle-shaped pores and becomes spot corrosion.

Because the Cl- ion has a small radius and strong penetrating power, it is easy to enter the passivation film, adsorb on the metal surface, and then form strong acid and weak alkali salts with Fe2+ ions generated by corrosion, making the microenvironment more acidic and accelerating Corrosion process.

The austenite structure content and ferrite structure content of stainless steel are duplex stainless steel. If you can search for the metallographic photos of duplex stainless steel, you can clearly see that black is ferrite and white is Austenitic, there are two phases in duplex stainless steel, which are distributed in layers. The existence of one phase prevents the development of cracks in the other phase. The cracks propagate in the ferrite phase and need to bypass the island-shaped austenite phase. , And the austenite phase acts as a barrier, so the duplex stainless steel tube is resistant to chloride ion corrosion.

Huzhou Nanxun Yintuo Special Material Technology Co., Ltd. is committed to the production of stainless steel seamless pipes. Austenitic stainless steel seamless tubes are especially favored by customers. If you are interested in our products, you are welcome to contact us.

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