An advanced form of intergranular corrosion is called what?

• A. Uniform Surface Corrosion
• B. Pitting
• C. Intergranular Corrosion
• D. Exfoliation Corrosion

Answer: (D)

Intergranular corrosion means the metal is attacked along the grain boundaries. When that attack becomes severe enough that corrosion products between the grains push the layers apart and the metal begins to peel away in sheets, you get exfoliation corrosion. This is the advanced form because it don’t just attack along boundaries; it causes a layered, flaky separation of material, which can lead to rapid loss of thickness and strength. You’ll often see flaky surface scales and delamination as the telltale signs. This differs from uniform surface corrosion, which uniformly thins the surface, and from pitting, which forms isolated pits, while plain intergranular corrosion is attack along boundaries without the peeling.