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Crevice corrosion is a localized form of corrosive attack. Crevice corrosion can occur between two metal surfaces or between metals and nonmetal surfaces at narrow openings or spaces such as: (reference)
Flanges
Deposits
Washers
Rolled tube ends
Threaded joints
O-rings
Gaskets
Lap joints
Sediment
A concentration cell forms with the crevice being depleted of oxygen. This differential aeration between the crevice (microenvironment) and the external surface (bulk environment) gives the the crevice an anodic character. This can contribute to a highly corrosive condition in the crevice. Crevice tests do not have to be complicated as demonstrated in an experiment designed to reveal the beneficial properties of corrosion preventive compounds (CPCs). A more standard test was also carried out to reveal the crevice resistance provided to steel by these commercial CPCs.
