What is the difference between pitting corrosion and intergranular corrosion?

Pointing corrosion refers to the pit-like corrosion form in which corrosion is concentrated in a local area on the metal surface and penetrates deep into the metal. That is, the location of corrosion thinning is point-like. Corresponding to it is large-area corrosion and uniform corrosion. Intergranular corrosion is a common localized corrosion. Corrosion develops along the grain boundaries of metal or alloy or in its adjacent areas. The grains themselves corrode very slightly. This kind of corrosion is called intergranular corrosion. This corrosion makes the bonding force between grains * * Weakened, in severe cases, the mechanical strength can be completely lost. For example, stainless steel that has suffered this kind of corrosion may still look bright on the surface, but it cannot withstand light knocks and breaks into fine particles. Since intergranular corrosion is difficult to detect, it can easily cause sudden damage to equipment and is very harmful. Stainless steel, nickel-based alloys, aluminum alloys, magnesium alloys, etc. are all materials with high sensitivity to intergranular corrosion. Use under heat or during welding can cause intergranular corrosion problems. With intergranular corrosion as the origin, under the combined action of stress and medium, stainless steel, aluminum alloys, etc. can induce intergranular stress corrosion, so intergranular corrosion is sometimes the precursor of stress corrosion. Under normal corrosion conditions, the grain boundary activity in the passivated alloy structure is not large, but when it is sensitive to intergranular corrosion, the intergranular activity is very large, that is, there is a certain potential difference between the lattice grains and the grain boundaries. This is mainly caused by the change in the structure of the alloy when the alloy is improperly heated. Therefore, intergranular corrosion is a kind of localized corrosion caused by electrochemical inhomogeneity of the tissue. In addition, when impurities exist at the grain boundaries, intergranular corrosion can also be caused in certain media. Pitting corrosion and intergranular corrosion are both types of local corrosion. Their main differences can be seen from the metallographic pictures of the corroded parts. Intergranular corrosion is along the grain, while pitting corrosion does not have this feature.

You can tell the difference based on the name. Pitting corrosion is punctate, while intergranular corrosion occurs along the intergranular space and is continuous.

What the 2nd floor said is great. I finally know that the crystal corrosion of stainless steel is also so important.

I understand, the difference is quite big.

Electrical corrosion is pitted corrosion, and intergranular corrosion is corrosion along the intergranular spaces.

Hello, I would like to ask which document this definition of intergranular corrosion is quoted from.