ASTM F1624 is a standard test method for measuring the hydrogen embrittlement threshold in steel using the incremental step loading (ISL) technique. It is commonly used when teams need a quantitative threshold for time-delayed cracking risk in high-strength steels after manufacturing processes (such as plating) or when exposed to hydrogen-generating service environments.
The standard supports practical decisions in design, process control, and failure analysis by helping labs compare susceptibility across materials, heat treatments, and hydrogen exposure conditions. If you need help mapping your part geometry and loading mode to an appropriate F1624 test setup, talk with our team.
ASTM F1624: Standard Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique
ASTM F1624 defines an incremental step loading approach for evaluating steel susceptibility to time-delayed failure associated with hydrogen. It can be applied using standard fracture mechanics specimens, notched specimens, or actual products such as fasteners and springs.
Quick Definition
ASTM F1624 measures a threshold for the onset of subcritical crack growth under stepwise loading, helping quantify hydrogen-embrittlement susceptibility in steel under either residual-hydrogen conditions (tested in air) or environmentally introduced hydrogen (tested in a controlled environment).
What This Standard Covers
This test method establishes a procedure to measure susceptibility to time-delayed failure such as that caused by hydrogen. The threshold is determined by increasing load in controlled steps and observing when subcritical cracking begins under the selected test conditions.
ASTM F1624 can be used to evaluate, quantitatively:
- Relative susceptibility of steels of different composition or heat treatment
- Effects of residual hydrogen from processing steps (for example, surface treatments, coatings, electroplating)
- Effects of hydrogen introduced from external sources during service exposure (for example, certain fluids/chemicals and aqueous conditions)
The test may be performed in air to evaluate residual hydrogen from processing or in a controlled environment to evaluate hydrogen uptake from the service environment.
Why This Standard Matters in Testing
Hydrogen-assisted cracking can produce delayed, brittle failures that are difficult to screen with conventional short-duration strength tests. ASTM F1624 is often selected when a program needs a quantitative limit that can be used to compare materials/processes or set operating/installation stress targets tied to hydrogen embrittlement risk.
Because results are sensitive to loading profile, specimen/product geometry, and exposure conditions, the exact edition cited on a drawing, purchase order, or qualification plan can materially affect how the test is configured and how data is interpreted.
Common Materials, Product Types, or Applications Covered
Common materials: Steels where hydrogen embrittlement susceptibility is a concern, especially higher-strength conditions.
Common product types: Fasteners (threaded or unthreaded), springs, and steel components that may retain hydrogen from processing or absorb hydrogen in service.
Common application drivers: Plating/coating process control, manufacturing qualification, service-environment screening, and root-cause work tied to delayed cracking.
Common Test or Verification Workflow
While the detailed sequence is defined in the standard itself, most ASTM F1624 programs follow a workflow like this:
- Select the specimen type or actual product geometry appropriate to the question being asked (fracture mechanics specimen, notched specimen, or product such as a fastener).
- Define whether the intent is to evaluate residual hydrogen from processing (testing in air) or hydrogen uptake from an external environment (testing in a controlled environment).
- Apply incremental load steps with defined holds until evidence of subcritical cracking/failure behavior establishes a threshold under the selected conditions.
- Report threshold results alongside the key test conditions (material condition, geometry, loading mode, environment, and step-loading parameters) so results can be compared and used for acceptance, ranking, or engineering assessment.
Equipment Commonly Used for This Standard
ASTM F1624 is equipment-driven: success depends on stable load control over step holds, repeatable fixturing, and (when required) controlled exposure conditions.
Common equipment: Servo-hydraulic or electromechanical universal testing systems capable of controlled step loading and timed holds; load cells sized for the expected threshold; fixtures/grips matched to the chosen specimen or product geometry (including fastener- or notched-specimen fixturing).
Environment options (when required): Controlled-environment hardware appropriate to the intended hydrogen source (for example, an environmental enclosure or dedicated exposure setup), integrated in a way that maintains safe operation and consistent loading alignment.
If you are comparing test frame capacities, control packages for step-hold loading, or fixturing for fasteners and notched specimens, you can request a detailed quote for an ASTM F1624-capable configuration.
How to Read This Designation or Revision
ASTM standards are typically cited with the designation and an edition year. For example, current edition records for this standard include a designation in the form ASTM F1624-12(2024), where the earlier year indicates the base edition and the year in parentheses indicates a later reapproval year.
Because step-loading parameters, reporting expectations, and annex guidance can change across editions, purchase specifications and qualification plans should always state the exact cited version to be used for testing and reporting.
Related Standards, Methods, or Frameworks
ASTM F1624 is often used alongside broader hydrogen embrittlement control and evaluation programs for steel parts and fasteners. The standard also references common industry documents for certain product types (for example, fastener-related SAE documents referenced within the scope).
When a customer requirement references multiple hydrogen embrittlement methods, the key practical task is aligning specimen/product geometry, exposure condition (air vs controlled environment), and acceptance logic across the cited documents—without mixing test intents or reporting conventions.
Need help selecting an ASTM F1624 test system?
If you want to run ASTM F1624 with step-hold loading control, appropriate fixturing for your specimen or fastener geometry, and an environment approach matched to your use case, contact our team to discuss a practical configuration.