Hydrogen embrittlement

Risk of hydrogen embrittlement

Hydrogen embrittlement of high strength bolts of property classes 10.9 and 12.9 is a change in material behavior by atomic hydrogen which can lead to brittle fracture under tensile load caused by the tightening procedure or in service conditions. According to DIN EN ISO 4042, which describes electroplating of threaded parts like bolts, there is a risk of hydrogen embrittlement for all fasteners with hardness above 320 HV. Also other parts with hardness above 320 HV have a risk of hydrogen embrittlement, even when this hardness values only occur locally.

Considering this fastener producers conduct activities regarding the manufacturing processes, especially of electroplated fasteners, that minimize the risk of hydrogen embrittlement. These activities are the condition for a supplier approval for high strength fasteners of property class 10.9 and 12.9.

Even following all rules according to the state of the art processes to minimize the risk of hydrogen embrittlement, a guarantee for the complete elimination of that risk cannot be given, especially because influences of service condition in application take place e.g. corrosion.

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