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Phone: +86 13679287344
E-mail: [email protected]
Add: Room1102, Land Center T1, Yanzhan Road, No. 1111, Qujiang New District, Xi'an, China.
What is Hydrogen Embrittlement in Bolts? Risks & Prevention for High Strength Fasteners
Time: 2026-08-14 Source: Author:
Sudden bolt breakage without obvious external impact often puzzles engineers and purchasers working on steel structures, wind power equipment, construction machinery, and new energy projects. In most cases, this unexpected failure is caused by hydrogen embrittlement. Many buyers lack sufficient awareness of this hidden risk, which may lead to severe safety hazards for the whole project.
1. What is Hydrogen Embrittlement?
Hydrogen embrittlement is also known as hydrogen-induced cracking.
During manufacturing processes such as pickling and electroplating, hydrogen atoms penetrate the interior of steel. Under sustained mechanical stress, hydrogen accumulates along grain boundaries and forms tiny internal cracks. These cracks expand gradually and finally result in abrupt brittle fracture of bolts.
Key characteristics of hydrogen embrittlement failure:
Brittle fracture with almost no plastic deformation; difficult to detect visually in advance.
Breakage may occur within several hours or even months after installation and tightening.
Higher strength bolts have much higher susceptibility to hydrogen embrittlement.
Bolts of grade 10.9 and 12.9 are at high risk, while grade 8.8 and below are far less sensitive.
2. Main Sources of Hydrogen Leading to Bolt Embrittlement
Surface treatment processes
Pickling for rust removal and electroplating are the most common triggers. A large amount of hydrogen invades the steel substrate during electroplating. If post-plating baking for hydrogen removal is inadequate, residual hydrogen remains inside the bolt.
Raw material and heat treatment defects
Excessive hydrogen content in steel wire rod caused by smelting or improper heat treatment procedures.
Corrosive service environment
When bolts are continuously exposed to humid, saline, or marine atmosphere, corrosion reactions continuously generate hydrogen atoms that penetrate the metal.
3. Potential Engineering Consequences
Hydrogen embrittlement triggers sudden bolt failure. Broken connection bolts on wind turbine towers, steel structure joints, or machinery chassis may cause structural instability and equipment collapse. For wind power, bridge, and heavy machinery projects, such failures result in serious safety accidents and massive economic losses.
A common misunderstanding: Many customers believe bolts pass tensile testing and look intact, so they are safe. Conventional tensile tests cannot effectively screen hydrogen embrittlement risks.
4. Effective Solutions to Prevent Hydrogen Embrittlement
✅ Select proper surface coating
High-strength bolts are recommended to adopt hot-dip galvanizing, Dacromet coating or mechanical galvanizing. Ordinary electroplating should be avoided when possible. If electroplating is required, strict hydrogen removal baking is mandatory.
✅ Standard hydrogen relief treatment
Conduct baking immediately after electroplating: typically 200–230°C for 2–4 hours to drive out hydrogen trapped inside steel.
✅ Carry out batch inspection
Implement delayed fracture testing or constant load testing for random sampling of bulk orders.
✅ Optimize product selection
For high-stress, corrosive outdoor working conditions, consult manufacturers to optimize material and coating schemes. Avoid matching high-strength bolts with high-risk electroplating processes.
5. Tips for Purchasers
When sourcing high-strength bolts, apart from mechanical test reports, confirm the following with your fastener supplier:
Complete standardized surface treatment procedures
Hydrogen removal process implemented for electroplated high-strength bolts
Availability of hydrogen embrittlement-related test support
Conclusion
Hydrogen embrittlement is a critical technical issue that cannot be ignored for high-strength fasteners. Qualified bolts need to meet tensile standards, and manufacturers must control hydrogen risks through the whole production chain: raw material inspection, heat treatment, and surface finishing.
LJBolt manufactures Grade 8.8, 10.9, and 12.9 high-strength bolts, structural bolts, and custom fasteners for the wind power industry. We strictly control heat treatment and surface treatment processes, and provide professional anti-hydrogen embrittlement solutions for high-stress applications. Complete material certificates and test reports are available. Welcome global customers for samples and bulk orders.
1. What is Hydrogen Embrittlement?
Hydrogen embrittlement is also known as hydrogen-induced cracking.
During manufacturing processes such as pickling and electroplating, hydrogen atoms penetrate the interior of steel. Under sustained mechanical stress, hydrogen accumulates along grain boundaries and forms tiny internal cracks. These cracks expand gradually and finally result in abrupt brittle fracture of bolts.
Key characteristics of hydrogen embrittlement failure:
Brittle fracture with almost no plastic deformation; difficult to detect visually in advance.
Breakage may occur within several hours or even months after installation and tightening.
Higher strength bolts have much higher susceptibility to hydrogen embrittlement.
Bolts of grade 10.9 and 12.9 are at high risk, while grade 8.8 and below are far less sensitive.
2. Main Sources of Hydrogen Leading to Bolt Embrittlement
Surface treatment processes
Pickling for rust removal and electroplating are the most common triggers. A large amount of hydrogen invades the steel substrate during electroplating. If post-plating baking for hydrogen removal is inadequate, residual hydrogen remains inside the bolt.
Raw material and heat treatment defects
Excessive hydrogen content in steel wire rod caused by smelting or improper heat treatment procedures.
Corrosive service environment
When bolts are continuously exposed to humid, saline, or marine atmosphere, corrosion reactions continuously generate hydrogen atoms that penetrate the metal.
3. Potential Engineering Consequences
Hydrogen embrittlement triggers sudden bolt failure. Broken connection bolts on wind turbine towers, steel structure joints, or machinery chassis may cause structural instability and equipment collapse. For wind power, bridge, and heavy machinery projects, such failures result in serious safety accidents and massive economic losses.
A common misunderstanding: Many customers believe bolts pass tensile testing and look intact, so they are safe. Conventional tensile tests cannot effectively screen hydrogen embrittlement risks.
4. Effective Solutions to Prevent Hydrogen Embrittlement
✅ Select proper surface coating
High-strength bolts are recommended to adopt hot-dip galvanizing, Dacromet coating or mechanical galvanizing. Ordinary electroplating should be avoided when possible. If electroplating is required, strict hydrogen removal baking is mandatory.
✅ Standard hydrogen relief treatment
Conduct baking immediately after electroplating: typically 200–230°C for 2–4 hours to drive out hydrogen trapped inside steel.
✅ Carry out batch inspection
Implement delayed fracture testing or constant load testing for random sampling of bulk orders.
✅ Optimize product selection
For high-stress, corrosive outdoor working conditions, consult manufacturers to optimize material and coating schemes. Avoid matching high-strength bolts with high-risk electroplating processes.
5. Tips for Purchasers
When sourcing high-strength bolts, apart from mechanical test reports, confirm the following with your fastener supplier:
Complete standardized surface treatment procedures
Hydrogen removal process implemented for electroplated high-strength bolts
Availability of hydrogen embrittlement-related test support
Conclusion
Hydrogen embrittlement is a critical technical issue that cannot be ignored for high-strength fasteners. Qualified bolts need to meet tensile standards, and manufacturers must control hydrogen risks through the whole production chain: raw material inspection, heat treatment, and surface finishing.
LJBolt manufactures Grade 8.8, 10.9, and 12.9 high-strength bolts, structural bolts, and custom fasteners for the wind power industry. We strictly control heat treatment and surface treatment processes, and provide professional anti-hydrogen embrittlement solutions for high-stress applications. Complete material certificates and test reports are available. Welcome global customers for samples and bulk orders.
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