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ISO / TR 20491 – Hydrogen embrittlement in steel fasteners

The publication of ISO/TR 20491 by CEN has resulted in questions regarding hydrogen embrittlement and the need to avoid it in bolts of property class 10.9. The technical report is the basis for the changes that have been implemented in the latest revision of  BS EN ISO4042:2018 with regards to the  de-embrittle property class 10.9 bolts.

BSI FME 9, the fastener technical committee , recommended in its National Foreword that regardless of the changes in BS EN ISO4042:2018 that all electroplated 10.9 bolts should be hydrogen de-embrittled; the committee also agreed not to publish the technical report ISO/TR20491 in the UK.

The BCSA’s Fastener Working Group  also decided to make hydrogen de-embrittlement a requirement of all coated property class 10.9 bolts in the BCSA’s ‘MODEL SPECIFICATION for the PURCHASE of STRUCRURAL BOLTING ASSEMBLIES and HOLDING DOWN BOLTS’.

Thomas Cosgrove 

BCSA Fabrication & Welding Manager.

Tel: 07525 986700