Intergranular corrosion is corrosion that forms within the metal along grain structures.

Intergranular corrosion is corrosion that forms within the metal along grain structures.

• A. Within the metal grains
• B. On external surfaces only
• C. Along the grain boundaries
• D. In the protective coating

Answer: (C)

Intergranular corrosion occurs at the interfaces where individual crystal grains meet in a metal. Those grain boundaries are regions of higher energy and often host impurities or precipitates that make them more susceptible to attack, so the corrosion propagates along those boundaries rather than through the grain interiors. That’s why describing it as along the grain boundaries is the correct choice. If corrosion happened inside the grains, that would be intragranular corrosion. If it were only on external surfaces, it wouldn’t specifically involve the grain structure. If it were in a protective coating, the issue would be coating degradation rather than corrosion along metal grain boundaries.

Intergranular corrosion occurs at the interfaces where individual crystal grains meet in a metal. Those grain boundaries are regions of higher energy and often host impurities or precipitates that make them more susceptible to attack, so the corrosion propagates along those boundaries rather than through the grain interiors. That’s why describing it as along the grain boundaries is the correct choice.

If corrosion happened inside the grains, that would be intragranular corrosion. If it were only on external surfaces, it wouldn’t specifically involve the grain structure. If it were in a protective coating, the issue would be coating degradation rather than corrosion along metal grain boundaries.