Which term describes corrosion that occurs along the grain boundaries within a metal?

Which term describes corrosion that occurs along the grain boundaries within a metal?

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

Answer: (B)

Corrosion that travels along the grain boundaries is called intergranular corrosion. In metals with crystal grains, the boundaries between those grains can be more electrochemically active than the grain interiors. This can happen when alloying elements segregate or precipitate at the boundaries, or when heat treatment causes sensitization (for example, chromium carbides forming at grain boundaries in stainless steels). Because the boundaries become a preferred path for corrosion, the metal erodes along these lines rather than evenly across the surface. Think of it as a highway along the seams between crystals, rather than a uniform rain on the entire surface. Uniform surface corrosion would affect the whole surface more or less evenly; pitting forms isolated tiny holes rather than a continuous boundary path. Exfoliation corrosion is a form of intergranular damage that can cause layers to peel away along those boundaries, but the broad term for corrosion specifically along grain boundaries is intergranular corrosion.

Corrosion that travels along the grain boundaries is called intergranular corrosion. In metals with crystal grains, the boundaries between those grains can be more electrochemically active than the grain interiors. This can happen when alloying elements segregate or precipitate at the boundaries, or when heat treatment causes sensitization (for example, chromium carbides forming at grain boundaries in stainless steels). Because the boundaries become a preferred path for corrosion, the metal erodes along these lines rather than evenly across the surface.

Think of it as a highway along the seams between crystals, rather than a uniform rain on the entire surface. Uniform surface corrosion would affect the whole surface more or less evenly; pitting forms isolated tiny holes rather than a continuous boundary path. Exfoliation corrosion is a form of intergranular damage that can cause layers to peel away along those boundaries, but the broad term for corrosion specifically along grain boundaries is intergranular corrosion.