Kärjekorrosioon

Kärjekorrosioon, also known as pitting corrosion, is a localized form of corrosion that leads to the formation of small holes or pits in metal surfaces. This type of corrosion is particularly insidious because it can cause significant damage even with a relatively small amount of metal loss. Pitting is most common in environments that contain aggressive ions, such as chlorides, which are found in saltwater, some industrial chemicals, and de-icing salts.

The mechanism behind pitting corrosion often involves a breakdown of the passive film that normally protects the metal surface. Once a small defect occurs in this film, a localized electrochemical cell can form. Anodic dissolution of the metal occurs within the pit, while the surrounding area acts as the cathode. The pit often becomes filled with corrosion products, which can further concentrate the aggressive ions and accelerate the corrosion process.

Factors that influence the initiation and propagation of pitting corrosion include the metal's composition and microstructure, the presence and concentration of corrosive species, temperature, and flow conditions. Stainless steels, aluminum alloys, and copper alloys are susceptible to pitting under certain conditions. The severity of pitting can range from superficial pits to deep, penetrating holes that can compromise the structural integrity of the component. Detecting and preventing pitting corrosion is crucial in many industries, including chemical processing, marine engineering, and oil and gas. Regular inspection and the use of corrosion-resistant materials or protective coatings are common strategies.