Exfoliation corrosion occurs most clearly at which area of the metal?

Exfoliation corrosion occurs most clearly at which area of the metal?

• A. Grain boundaries
• B. Surface
• C. Subsurface
• D. Coatings

Answer: (A)

Exfoliation corrosion is most clearly seen along grain boundaries. These boundaries are where the crystal lattice is disrupted and often have segregated elements or precipitates that create galvanic differences between neighboring grains. This makes dissolution more favorable along the boundaries than through the grain interiors. As corrosion products form at these boundaries and expand, they push apart the layers of metal, producing the characteristic peeling or laminar sheets that run parallel to the surface. The surface may show the effects, but the damage originates and propagates along the grain boundaries just beneath or at the surface, making that area the key region for exfoliation. Coatings can influence overall corrosion behavior, but exfoliation itself is driven by intergranular attack at the boundaries, not by the surface alone or by coatings.

Exfoliation corrosion is most clearly seen along grain boundaries. These boundaries are where the crystal lattice is disrupted and often have segregated elements or precipitates that create galvanic differences between neighboring grains. This makes dissolution more favorable along the boundaries than through the grain interiors. As corrosion products form at these boundaries and expand, they push apart the layers of metal, producing the characteristic peeling or laminar sheets that run parallel to the surface. The surface may show the effects, but the damage originates and propagates along the grain boundaries just beneath or at the surface, making that area the key region for exfoliation. Coatings can influence overall corrosion behavior, but exfoliation itself is driven by intergranular attack at the boundaries, not by the surface alone or by coatings.