Crevice corrosion is a form of localized attack in which the size of the attack is an area where free access to the surrounding environment is restricted.

• A. Pitting corrosion
• B. Crevice corrosion
• C. Uniform corrosion
• D. Galvanic corrosion

Answer: (B)

Crevice corrosion is a localized attack that occurs where access to the surrounding environment is restricted, such as under gaskets, deposits, or crevices around fasteners. In these confined spaces, diffusion of oxygen is limited, creating a differential aeration cell: the metal inside the crevice becomes anodic and dissolves, while the exterior acts as the cathode. The restricted flow also concentrates aggressive ions, accelerating corrosion within the crevice. This confinement makes the damage appear localized rather than spread evenly across the surface, which is the hallmark that sets it apart from uniform corrosion. While pitting is also localized, it isn’t defined by restricted access, and galvanic corrosion arises from electrical potential differences between dissimilar metals rather than from a restricted environment.