Exfoliation corrosion occurs along grain boundaries and causes which result?

• A. Delamination along grain boundaries
• B. Pitting at grain centers
• C. Uniform thinning across surface
• D. Cracking parallel to surface

Answer: (A)

Exfoliation corrosion is an intergranular form of attack where the grain boundaries become the preferred path for corrosion. Because the boundaries are weaker and often have impurities or different electrochemical behavior than the grain interiors, the metal along these boundaries corrodes more rapidly. This causes the layers of material to separate and peel away in thin sheets that run parallel to the surface. The result is delamination along the grain boundaries.

Pitting at grain centers would be localized inside grains, not along boundaries. Uniform thinning would be even loss across the surface, not layered delamination. Cracking parallel to the surface describes a different failure mode, not the sheet-like peeling seen with exfoliation.