Crevicekorroosio

Crevice corrosion is a localized form of corrosion that occurs within confined spaces or crevices. These crevices can form in areas where dissimilar materials are joined, under deposits, gaskets, or bolt heads, or in any situation where an electrolyte can be trapped. The unique electrochemical conditions within these narrow gaps distinguish crevice corrosion from general corrosion.

The process typically begins with the depletion of oxygen within the crevice. As oxygen levels decrease, the cathodic reaction (usually oxygen reduction) slows down or stops. However, the anodic reaction (metal oxidation) continues, leading to the dissolution of metal within the crevice. This dissolution releases metal ions into the electrolyte.

To maintain charge neutrality, anions from the surrounding electrolyte, such as chloride ions (Cl-), migrate into the crevice to balance the positive charge of the metal ions. Simultaneously, hydrogen ions (H+) are generated or attracted into the crevice, further lowering the pH. This acidic and chloride-rich environment aggressively attacks the metal, accelerating the corrosion process.

Factors influencing crevice corrosion include the geometry of the crevice, the materials involved, the temperature, and the composition of the electrolyte. Stainless steels, aluminum alloys, and titanium are susceptible to crevice corrosion, especially in chloride-containing environments like seawater. Mitigation strategies often involve designing components to avoid crevices, using appropriate materials, and maintaining clean surfaces.