The lifting or flaking of metal at the surface due to delamination of grain boundaries caused by buildup of corrosion products is called what?

• A. Exfoliation
• B. Spalling
• C. Peeling
• D. Flaking

Answer: (A)

Exfoliation is a corrosion mechanism where layers of metal peel away in sheets parallel to the surface due to corrosion products forming between grains and driving delamination along grain boundaries. The buildup of these products—often under tensile stress—pries the layers apart, producing lifted, flaky sheets that are characteristic of exfoliation. This is a distinct, specific term for this layered delamination, unlike generic terms such as peeling or flaking or processes like spalling, which describe other kinds of surface failure without the same grain-boundary delamination mechanism.