What is intergranular corrosion in metal material?
When the stainless steel pipe fittings or forged steel flange products are manufactured in our factory,we should keep attention to the intergranular corrosion of such piping products.The microstructure of metals and alloys are made up of grains,and they are separated by grain boundaries. Intergranular corrosion is localized attack along the grain boundaries,attacking the surface of the metal or alloy,it is also called intergranular attack.
This kind of corrosion weakens the binding force between grains and completely loses the mechanical strength. For example, the surface of the stainless steel suffering from such corrosion looks bright, but it can’t stand to be broken into fine particles with a little tap. Because intergranular corrosion is not easy to check, the sudden breaking of civil equipment is very harmful.
Stainless steel, nickel base alloy, aluminum alloy and magnesium alloy are all materials with high sensitivity to intergranular corrosion. Intergranular corrosion can be caused by using or welding under the condition of heating. Intergranular corrosion, which originates from intergranular corrosion, can induce intergranular stress corrosion of stainless steel and aluminum alloy under the joint action of stress and medium.
Under normal corrosion conditions, the intergranular activity of passivated alloy is not very high, but when it has the sensitivity of intergranular corrosion, the intergranular activity is very high, that is, there is a certain potential difference between the lattice particles and the grain boundary, which is mainly caused by the change of structure when the alloy is not heated properly.
Therefore, intergranular corrosion is a kind of local corrosion caused by the electrochemical inhomogeneity of the structure. In addition, intergranular corrosion can also be caused by impurities in the grain boundary.