Crevice corrosion occurs where?

• A. In the bulk metal interior
• B. On open surfaces
• C. Only under high humidity conditions
• D. Within crevices where the electrolyte becomes stagnant; minimize by eliminating crevices, using seals, and avoiding deposits.

Answer: (D)

Crevice corrosion is a localized attack that starts in restricted spaces where an electrolyte can become stagnant and oxygen supply is limited. In these crevices, a differential environment develops: the interior of the crevice becomes anodic while the exterior is relatively cathodic, driving a concentration-cell corrosion that accelerates attack right inside the crevice. This is why corrosion commonly occurs under gaskets, deposits, fastener holes, or any narrow gap where water and salts can accumulate and remain stagnant. The recommended mitigation—eliminating crevices, using seals, and avoiding deposits—prevents the trapped, stagnant electrolyte that drives the process. Open or bulk metal surfaces don’t create the same localized electrochemical conditions, and while high humidity can worsen corrosion, the defining situation for crevice corrosion is the stagnant electrolyte within a crevice, not humidity alone.