Väkirymäkorroosio

Väkirymäkorroosio, also known as crevice corrosion, is a localized form of corrosion that occurs in narrow gaps or crevices where stagnant solution can accumulate. This environment is often found in areas where components are joined, such as under gaskets, bolt heads, or in overlapping metal plates. The unique conditions within the crevice lead to a difference in the electrochemical potential between the metal inside the crevice and the metal exposed to the bulk environment.

The process typically begins with the hydrolysis of metal ions that form in the crevice. This releases hydrogen ions, making the solution within the crevice more acidic. Simultaneously, the consumption of oxygen within the crevice leads to a more oxygen-depleted area compared to the surrounding, freely exposed metal. This difference in oxygen concentration drives the corrosion process, as the oxygen-depleted area within the crevice becomes the anode and the more oxygenated area outside becomes the cathode.

Väkirymäkorroosio can be particularly damaging because it is often hidden from view and can lead to rapid material degradation. The rate of corrosion can be significantly higher than general corrosion. Factors influencing its severity include the material's susceptibility to corrosion, the geometry of the crevice, the composition of the corrosive environment (especially chloride ions), temperature, and the duration of exposure. Common materials susceptible to crevice corrosion include stainless steels, aluminum alloys, and titanium alloys, especially in chloride-containing environments like seawater. Prevention strategies involve minimizing crevices, using appropriate materials, maintaining protective coatings, and controlling the operating environment.