Crevice corrosion is a particular form of localized corrosion which occurs in a crevice formed between two surfaces, at least one of which
is a metal. It can also be a particular form of pitting which occurs between facing surfaces (e.g., in threaded or flanged connections), usually due to oxygen
concentration cell effects. The lower oxygen content in the crevice helps create an anode at the metal surface.
Key Properties of Crevice Corrosion
- Is found in isolated or stagnant zones such as under gaskets, skip weld joints, and crevices.
- Oxidation occurs within the crevice, while reduction occurs in the open zone.
- Metal ions continue to go into solution at the oxidation zone (anode).
- The resulting imbalance creates an anodic region (crevice) and a cathodic region (open zone).
- It can become auto catalytic and can result in rapid and deep pitting.
- Stainless steels are particularly susceptible to crevice corrosion.
Where does it occur?
- Under gaskets
- Flanges
- Lap joints
- Bolted connections
- Under deposits
How to Control Crevice Corrosion?
Crevice corrosion may be controlled in a variety of ways, including:
- Use welded butt joints instead of riveted or bolted joints.
- Close crevices in existing lap joints by continuous welding, caulking or soldering.
- Design vessels for complete drainage and avoid stagnant areas.
- Remove deposits frequently.
- Remove wet packing materials during long shutdowns.
- Use non-absorbent gaskets.
- Use materials resistant to crevice corrosion.
- Use protective coatings.
Source: Chesterton ARC Manuals
« Back to Glossary Index