What is intergranular corrosion?


    Austenitic stainless steel refers to stainless steel with an austenitic structure at room temperature. When the steel contains about 18% Cr, 8%-10% Ni, and about 0.1% C, it has a stable austenite structure.

    The characteristic of austenitic stainless steel is that in addition to the corrosion resistance of the oxidizing acid medium, if it contains elements such as Mo and Cu, it can also resist the corrosion of sulfuric acid, phosphoric acid, formic acid, acetic acid, uric acid, etc. If the carbon content in this type of steel is less than 0.03% or contains Ti and Ni, its resistance to intergranular corrosion can be significantly improved. High-silicon austenitic stainless steel has good corrosion resistance to concentrated nitric acid. As austenitic stainless steel has comprehensive and good comprehensive properties, it has been widely used in various industries.

    Intergranular corrosion is common localized corrosion, which extends to the inside along the interface between metal grains. The stainless steel subjected to this corrosion has a bright surface, but it will break into fine particles if it cannot withstand knocks. IGC destroys the bond between the crystal grains and greatly reduces the mechanical strength of the metal. Because the intergranular corrosion is not easy to inspect and causes sudden damage to the equipment, it is extremely harmful. Statistics believe that this type of corrosion accounts for about 10.2% of the total corrosion types.

    Austenitic stainless steel is one of the most widely used stainless steel in the industry. It is mostly within the sensitization temperature range of about 427℃-816℃. Intergranular corrosion is prone to occur in specific corrosive environments, and intergranular corrosion will also accelerate overall corrosion.

    The practice has shown that proper solution treatment, stabilization treatment, reduction of the content of carbon and impurity elements in the grain boundaries of austenitic stainless steel, elimination or prevention of the influence of the material during hot or cold working, etc., are all to reduce IGC sensitivity and Effective measures to prevent IGC.

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