Sprekkerorrosjon

Sprekkerorrosjon is a form of localized corrosion that occurs in narrow gaps, crevices, or under deposits where stagnant electrolyte can accumulate. This confined space restricts the flow of the bulk corrosive environment, leading to a difference in the electrochemical conditions within the crevice compared to the exterior surface. Typically, the crevice environment becomes more aggressive, accelerating the corrosion rate.

The mechanism of sprekkerorrosjon involves differential aeration. The limited access of oxygen into the crevice leads to the depletion of dissolved oxygen within the crevice. This oxygen-depleted area becomes the anode, while the exterior surface, with better access to oxygen, acts as the cathode. Metal ions dissolve at the anode within the crevice, and these ions can hydrolyze, releasing hydrogen ions and lowering the pH. The dissolved metal ions and the acidic environment further promote metal dissolution.

Common locations for sprekkerorrosjon include bolted joints, gasketed areas, under dislodged protective coatings, and in overlapping metal sheets. Materials susceptible to sprekkerorrosjon include stainless steels, aluminum alloys, and titanium alloys, especially in chloride-containing environments.

Preventing sprekkerorrosjon involves eliminating or minimizing crevices, ensuring good drainage to prevent stagnant water, maintaining protective coatings, and using materials with higher resistance to this type of corrosion in susceptible applications. Regular inspection and cleaning of equipment can also help identify and address potential sites of sprekkerorrosjon before significant damage occurs.