ISO 24251-1:2025

Overview - ISO 24251-1:2025 in brief

ISO 24251-1:2025, "Prevention of hydrogen assisted brittle fracture of high‑strength steel components - Part 1: Fundamentals and measures," provides guidance to reduce the risk of hydrogen embrittlement (HE) in components made from high‑strength steels (typically Rm > 1000 MPa). The standard addresses HE arising from manufacturing processes or service environments (excluding applications under pressurised hydrogen) and explains the interrelationship of material selection, manufacturing/heat treatment and coatings to prevent hydrogen‑assisted brittle fracture.

Key topics and technical focus

The standard organizes fundamentals and preventative measures across several technical areas:

• Fundamentals of hydrogen embrittlement: definitions (HE, IHE, EHE), mechanisms, and conditions required for brittle fracture (material susceptibility, tensile stress, hydrogen sources).
• Hydrogen diffusion and trapping: how atomic hydrogen migrates, interacts with microstructural traps (dislocations, inclusions, grain boundaries) and effuses from parts.
• Material selection and heat treatment: role of metallurgical state, quenching/tempering, case hardening, stress relief and baking in altering susceptibility.
• Stress management: importance of reducing residual tensile stress (stress relief) and managing applied stresses to stay below HE threshold stresses.
• Coatings and surface processes: fundamentals of metallic coatings, electroplating, pre‑treatment/cleaning, stripping and their influence on hydrogen uptake; corrective measures such as baking after coating.
• Environmental controls: design and operational measures to limit environmental hydrogen uptake and stress corrosion cracking.
• Informative annexes cover electroplating processes and principles of electrochemical corrosion.

Practical applications - who uses ISO 24251-1

This part of ISO 24251 is practical guidance for stakeholders across the steel and manufacturing supply chain who need to manage HE risk:

• Steel mills and material suppliers - specifying alloy and heat‑treatment options that minimise susceptibility.
• Component designers and OEMs - designing parts to reduce stress concentrators and specify appropriate treatments.
• Manufacturers and heat‑treatment shops - implementing quench/temper, stress relief, and baking procedures.
• Coaters and electroplaters - adopting pre‑treatment, plating and post‑treatment practices to avoid hydrogen uptake.
• Asset owners, inspectors and engineers - evaluating failure modes, choosing corrective actions and ensuring compatibility of coatings and processes.

Related standards and notes

• Normative reference: ISO 2080 (coating vocabulary).
• See also ISO 14713-2 for guidance on hot‑dip galvanizing components.
• Definitions reference documents such as ISO 1891‑2 where applicable.

Keywords: ISO 24251-1, hydrogen embrittlement, high‑strength steel, hydrogen assisted brittle fracture, electroplating, heat treatment, stress relief, baking, hydrogen diffusion.