ASTM B850
Standard Guide for Post-Coating Treatments of Steel for Reducing the Risk of Hydrogen Embrittlement
Guides selection of post-coating heat treatments for reducing hydrogen-embrittlement risk in steel parts.
What ASTM B850 specifies
ASTM B850 is a post-coating hydrogen-embrittlement relief guide, not a plating specification. It becomes relevant at actual tensile strengths of 1000 MPa or greater, approximately 31 HRC, and for surface-hardened parts. The common ER-1 through ER-9 series uses 190–220 °C with minimum times increasing from 8 hours at 1000–1100 MPa to 22 hours at 1701–1800 MPa. Treatment should start preferably within 1 hour and no later than 3 hours after plating. The guide warns that baking reduces risk but cannot guarantee complete freedom from hydrogen damage.
ASTM B850 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Requirement / test |
|---|---|---|
ER-9 | Steel with actual tensile strength 1000–1100 MPa. | 190–220 °C for at least 8 h. |
ER-8 | Steel with actual tensile strength 1101–1200 MPa. | 190–220 °C for at least 10 h. |
ER-6 to ER-1 | Strength bands from 1201–1300 through 1701–1800 MPa. | 190–220 °C for 12, 14, 16, 18, 20, or 22 h as strength increases. |
ER-13 | Unpeened and engineering-chromium-plated items within the stated strength range. | 440–480 °C for at least 1 h where substrate permits. |
Tests and the drawing call-out
Tests the document imposes
- Verification of actual tensile strength or hardness
- Furnace temperature and time records after the whole part reaches temperature
- Elapsed time from plating to bake
- Hydrogen-embrittlement test when required by the coating specification
How to cite it
Drawing call-out
POST-PLATE BAKE PER ASTM B850, CLASS <ER-CLASS>, <TEMPERATURE> °C FOR <HOURS> H MIN, START WITHIN <TIME>Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Finishes specified to ASTM B850
Also referenced by: Cadmium Plating, Electrolytic Nickel Plating, Hard Chrome Plating, Zinc Plating, Zinc-Nickel Plating.
ASTM B850 — frequently asked
When is a B850 bake normally considered?
The guide identifies steel at 1000 MPa actual tensile strength or above, about 31 HRC, and surface-hardened parts as potentially requiring relief. The responsible engineer must select the class.
How soon should baking start?
Start preferably within 1 hour and no later than 3 hours after plating. Delay reduces the effectiveness of hydrogen removal.
Does baking eliminate hydrogen-embrittlement risk?
No. ASTM B850 expressly states that treatment does not guarantee complete freedom from hydrogen degradation.
ASTM B850 is copyrighted by ASTM International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗