Careers Alloy 625 Corrosion: Comprehensive Guide to Corrosion Behavior and Protection
Composition & Properties
Alloy 625 (UNS N06625) is a nickel-chromium-molybdenum alloy with added niobium that provides exceptional resistance to a wide range of corrosive environments.
Chemical Composition
| Element | Percentage | Role in Corrosion Resistance |
| Nickel (Ni) | 58.0 min | Base metal, provides general corrosion resistance |
| Chromium (Cr) | 20.0-23.0 | Forms protective oxide layer |
| Molybdenum (Mo) | 8.0-10.0 | Enhances pitting and crevice corrosion resistance |
| Niobium (Nb) | 3.15-4.15 | Stabilizes against sensitization |
| Iron (Fe) | 5.0 max | Balance element |
Corrosion Resistance Profile
Excellent Resistance To:
- Pitting corrosion
- Crevice corrosion
- Stress corrosion cracking
- Oxidation up to 1800°F (982°C)
- Chloride ion attack
Common Applications:
- Chemical processing equipment
- Nuclear power systems
- Marine/offshore equipment
- Aerospace components
- Heat exchangers
Common Corrosion Challenges
Key Considerations
While Alloy 625 offers exceptional corrosion resistance, proper material handling and environmental controls are essential for optimal performance.
Potential Issues
- Sensitization at certain temperature ranges
- Galvanic corrosion when coupled with less noble metals
- High temperature sulfidation
- Potential for hot cracking during welding
Prevention Measures
- Proper heat treatment procedures
- Controlled welding parameters
- Regular inspection and monitoring
- Proper surface preparation
Protection Solutions
HVTS Application
High Velocity Thermal Spray (HVTS) can be applied on top of Alloy 625, to mitigate the risk of corrosion. This solution provides:
- Enhanced corrosion resistance
- No heat affected zone
- Rapid application
- Cost-effective protection
- Immediate return to service
Case Study: SMARTGard®: HVTS Stops Alloy 625 Weld Overlay Corrosion in a WtE Boiler
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