Glossary

Crevice corrosion is a localized form of corrosion that occurs in narrow, confined spaces where oxygen and other environmental conditions become trapped, creating a chemical imbalance. These spaces—called crevices—can exist between two metal surfaces or between a metal and a nonmetal, such as under washers, gaskets, fastener heads, lap joints, or even beneath dirt and deposits.

The problem begins when a small volume of electrolyte (like saltwater or moisture) enters the crevice. Inside the tight space, oxygen becomes depleted because it cannot easily circulate. Meanwhile, the surrounding surface outside the crevice remains exposed to oxygen. This difference in oxygen concentration creates an electrochemical cell: the area inside the crevice becomes anodic (where metal dissolves), and the area outside becomes cathodic (where reduction occurs). As a result, the trapped electrolyte inside the crevice becomes more acidic and chloride-rich, accelerating metal dissolution.

Over time, this process leads to pitting, discoloration, and material loss concentrated within the crevice. It is particularly problematic because it can occur beneath apparently intact surfaces, making it difficult to detect until severe damage has occurred. Stainless steels, aluminum alloys, and other passive metals are especially susceptible to crevice corrosion when their protective oxide film is compromised in these oxygen-starved environments.

Common prevention methods include designing joints to minimize tight gaps, using non-absorbent gaskets, selecting corrosion-resistant alloys, and applying protective coatings or sealants. Maintaining clean surfaces and avoiding stagnant conditions also help reduce risk.

In summary, crevice corrosion occurs when oxygen-starved microenvironments form within tight spaces on metal surfaces, leading to localized chemical attack that can severely weaken fasteners and assemblies over time.