Crevice corrosion is favored by which condition?

• A. Restricted flow of material into and out of the joint
• B. High humidity
• C. Large cavities
• D. Absence of ions

Answer: (A)

Crevice corrosion happens when a crevice traps electrolyte and restricts its flow, creating a localized, diffusion-limited environment that drives a galvanic cell. Inside the narrow gap, solution becomes stagnant and the supply of oxygen is limited, while the exterior surface is more oxygen-rich. This differential aeration causes metal in the crevice to become anodic and preferentially dissolve, accelerating attack along the crevice walls. That restricted flow into and out of the joint is the key condition that makes crevice corrosion favorable. High humidity alone can promote general corrosion but doesn’t create the diffusion-limited crevice environment; large cavities don’t by themselves establish restricted flow; and absence of ions would deprive the system of the electrolyte necessary for corrosion to proceed.