Hydrogen embrittlemen

Which high-strength fasteners may be at risk of hydrogen embrittlement after platin?

Using the ISO 4042 plating process, the relevant standards have warned of the sensitivity of high-strength fasteners to hydrogen embrittlement, which can occur when such fasteners are combined with electroplated coatings as well as hot-dip galvanized coating treatments for:

  •  Bolts with strength class 10.9/12.9.
  •  Product hardness ≥ 320HV, such as elastic washers, disc washers, elastic pins, grounding gaskets, etc..



In most cases, cracking occurs in the transition phase from the bolt head to the shank of the bolt, and the surface direction of the crack tends to be on the inside of the bolt head. Other parts with hardnesses above 320 HV are also at risk of hydrogen embrittlement. This can be clearly seen by scanning electron microscopy as an intergranular crack, i.e. fracture along grain boundaries, and exhibits typical residual toughness characteristics such as the formation of white lines on the grains and gaps between the grains.