Crevice Corrosion Occurs in spaces to which the access of the working fluid from the environment is limited. These spaces are called crevices.
What is Crevice Corrosion?
Crevice corrosion refers to a localized form of corrosion that occurs in narrow crevices or gaps between two metal surfaces or between a metal surface and another material. It is initiated by the presence of stagnant or trapped corrosive agents, such as moisture, chlorides, or acids, within the crevice. The lack of oxygen or limited access to the crevice area inhibits the normal protective oxide film formation on the metal surface, leading to accelerated corrosion.
Crevice corrosion happens when water or other corrosive substances get trapped in small spaces or gaps on metal surfaces, like around nuts or rivet heads. If there is dust or sand on the surface, it creates a place for water to collect and cause corrosion. This can damage the metal and make it weaker or even break.
Crevice Corrosion | Materials And Corrosion Control
| Damage Mechanism | Crevice Corrosion |
| Damage Description | · Occurs in spaces to which the access of the working fluid from the environment is limited. These spaces are called crevices. · Examples of crevices are gaps and contact areas between parts, under gaskets or seals, inside cracks and seams, spaces filled with deposits and under sludge piles. |
| Affected Materials | · Carbon steel and stainless steels, aluminum and copper alloys. |
| Control Methodology | · Use butt -welded joints instead of riveted or bolted joints in new equipment. · Eliminate crevices from in existing lap joints by continuous welding or soldering. · Seal lap joints where they cannot be avoided. · Avoid skip welds. · Use solid, non-absorbent gaskets such as Teflon. · Select materials more resistant to crevice corrosion. · Clean deposit or sludges where some build up is unavoidable such in vessels and tanks subject to stagnant or low flow conditions. · Provide complete drainage. |
| Monitoring Techniques | · Visual Inspection |
| Inspection Frequency | · Annually |
| KPIs | · No visible sign of corrosion in known crevices · Absence of sludge or deposits |
| Reference Resources (Standards/GIs/BPs) | · ASTM G58 |
Atmospheric Corrosion | Materials And Corrosion Control(Opens in a new browser tab)
Hydrogen Embrittlement | Materials And Corrosion Control(Opens in a new browser tab)
Liquid Metal Embrittlement | Materials And Corrosion Control(Opens in a new browser tab)
Notes:
- Crevice corrosion is extremely dangerous because it is localized and can lead to component failure while the overall material loss is minimal.
- The initiation and progress of crevice corrosion can be difficult to detect.
- Crevice corrosion is initiated by changes in local chemistry within the crevice:
- Depletion of inhibitor in the crevice
- Depletion of oxygen in the crevice
- A shift to acid conditions in the crevice
- Build-up of aggressive ion species (e.g., chloride) in the crevice