Intergranular stress corrosion cracking (IGSCC) is defined as cracking that occurs along the grain boundaries of crystallites due to corrosion. This form of corrosion cracking is caused by a combination of tensile stresses on the material in the presence of corrosive conditions. When IGSCC is present within pipes, trenchless methods can be used to save the pipe structure by relining it or replacing it without trenching the surrounding ground.

Although sometimes physically visible, IGSCC usually requires microscopic examination in order to be positively identified.

This form of corrosion cracking can occur in otherwise corrosion-resistant metals and alloys due to depletion of the grain boundaries. The applied tensile stresses on the material may be in the form of direct tensile stress or residual tensile stresses (due to welding, heat treatment, machining and grinding).

The microscopic nature of these types of cracks means it is sometimes difficult to detect. Most of the surface area of the material remains intact with fine cracks penetrating the grain boundaries in an intergranular or transgranular pattern. Due to its microscopic nature, IGSCC is classified as a potentially catastrophic form of corrosion as material failure is difficult to predict and can occur unexpectedly.

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