What hydrogen embrittlement is
Hydrogen embrittlement (HE) is when hydrogen atoms enter hard steel, making it brittle so it can crack under tension below its rated load. It often appears hours to days after assembly, which makes it dangerous.
It mostly affects high-hardness steel (generally >320 HV / ~32 HRC, e.g. grade 10.9 and 12.9 bolts).
Where the hydrogen comes from
Hydrogen enters during surface prep and plating — acid pickling and electroplating generate hydrogen at the surface, some of which diffuses into the steel.
Baking (de-embrittlement)
The standard prevention is baking at ~190–220°C for 4–24 hours, started soon after plating (often within 1–4 hours), so hydrogen diffuses out before it causes damage.
Standards such as ASTM B850 / ISO 4042 give temperature/time guidance by hardness level.
Good practice
For high-hardness fasteners, specify baking on the work order up front and bake as soon as possible after plating. V.S. Heat Treatment offers a baking service with an oven that processes up to 800 kg per batch with continuous time and temperature logging, managing this step for HE-risk work to protect load-bearing parts.
FAQ
Which parts need baking?+
High-hardness steel (~32 HRC and up) that has been acid-pickled or electroplated — e.g. grade 10.9/12.9 bolts, springs, clips.
Can baking be delayed?+
No — bake as soon as possible after plating (often within hours); waiting too long risks damage already forming.
