Which corrosion form involves peeling away layers along grain boundaries and is considered an advanced intergranular attack?

Which corrosion form involves peeling away layers along grain boundaries and is considered an advanced intergranular attack?

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

Answer: (C)

Exfoliation corrosion is a type of intergranular attack where corrosion products build up between grains and push the layers apart, causing the metal to peel away in sheets. The description of peeling away layers along grain boundaries fits this form exactly, because the attack progresses along the boundaries and the pressure from corrosion products creates a delaminated, layered failure rather than just thinning a surface. This makes it an advanced intergranular phenomenon, since it combines boundary-specific attack with a delamination of layers, often in rolled or highly elongated-grain alloys where the layers can separate more readily. By contrast, uniform surface corrosion would thin the surface evenly, intergranular corrosion would attack along grain boundaries without the dramatic peeling, and pitting would produce localized holes rather than layered delamination.

Exfoliation corrosion is a type of intergranular attack where corrosion products build up between grains and push the layers apart, causing the metal to peel away in sheets. The description of peeling away layers along grain boundaries fits this form exactly, because the attack progresses along the boundaries and the pressure from corrosion products creates a delaminated, layered failure rather than just thinning a surface. This makes it an advanced intergranular phenomenon, since it combines boundary-specific attack with a delamination of layers, often in rolled or highly elongated-grain alloys where the layers can separate more readily. By contrast, uniform surface corrosion would thin the surface evenly, intergranular corrosion would attack along grain boundaries without the dramatic peeling, and pitting would produce localized holes rather than layered delamination.