What Does Crevice Corrosion Mean?
Crevice corrosion can be defined as an attack on a metal surface at or near a crevice or gap between two joining surfaces, either metal-to-metal or metal and non-metallic material. Crevice corrosion is confined to one metal at the localized area, close to the joining surface, and occurs at locations where oxygen cannot freely circulate.
These sites can be tight joints, under fastener heads, or where the pieces of metal are in close contact. The site is ideal for the corrosion when it is wide enough to allow in the corroding electrolyte and provide stagnant conditions where oxygen is used but not replenished.
Trenchlesspedia Explains Crevice Corrosion
Crevice corrosion occurs at specific physical features where a surface is partly shielded and there is a presence of stagnant solution at the interface with the shielded area.
It is initiated by a difference in concentration of some chemical constituents which sets up an electrochemical concentration cell. The oxygen content and pH are higher and chlorides are lower outside the crevice (cathode).
The chlorides concentrate inside the crevice (anode) along with pollutants and moisture from the environment, depleting the crevice of oxygen. The stainless steel is then rapidly attacked due to the formation of ferric chloride from ferrous ions.
Chloride stress corrosion cracking (CLSCC) initiates from these sites where active pitting or crevice corrosion is taking place.