Crevice Corrosion: The Hidden Threat and Its Mechanisms
In addition to surface corrosion , the integrity of metal structures can be threatened by a less visible but equally destructive form of corrosion: crevice corrosion. This specific type of corrosion occurs in narrow gaps where oxygen and moisture have limited access. In these hidden crevices, which are often overlooked, unique corrosive conditions develop that lead to accelerated material degradation. This crevice can occur in a seam as well as around screws.
Crevice corrosion is a phenomenon caused by differences in oxygen concentration within narrow crevices. Limited aeration and the presence of electrolytes, such as saltwater, promote the formation of local anodic (where corrosion occurs) and cathodic (where protection occurs) areas. These differing areas lead to an electrochemical imbalance, which drives corrosion.
The mechanisms of crevice corrosion damage the surface in several stages:
- The oxygen contained in the water is reduced throughout the crevice by the classic corrosion reaction.
- The area near the surface is supplied with fresh oxygen from the environment. In this area, oxygen reduction or electron uptake can therefore continue to occur, leading to the formation of a cathode.
- This reaction occurs to a lesser extent inside the gap, so that an anode forms there at which the metal is reduced; the electrons released migrate across the metal surface to the cathode.
- At the cathode, the electrons contribute to the formation of hydroxide ions and thus an alkaline electrolyte.
- The formation of an alkaline electrolyte accelerates the removal of metal ions from the interior of the gap.
The result is an electrochemical reaction that causes the metal to dissolve more rapidly in the anodic region. The ratio of the surface areas of the anode to the cathode is critical to this process. Cathodic corrosion protection can increase the potential difference at the end of the gap—that is, at the anode—and thus accelerate the reaction.
PFINDER’s cavity protection or cavity preservation is formulated so that it can penetrate even the deepest and narrowest crevices. It seals these areas, forming a barrier against water or electrolytes, preventing them from entering and thereby reducing the potential difference. In addition to cavity protection, the corrosion protection wax can also be used in the field of corrosion protection for screws and other joining techniques.
PFINDER’s commitment to the fight against corrosion is reflected in the continuous improvement of our cavity preservation solutions. Our expertise and innovations in corrosion prevention enable us to respond individually to each customer’s needs and find customized solutions that go beyond standard applications.
Discover with us the power of our research and the strength of our products. Let’s work together to protect your projects from the invisible but serious threat of crevice corrosion.