Understanding Hydrogen Embrittlement:

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Hydrogen Embrittlement learn all about it.

How Does Hydrogen Interact with Steel?
- Even at room temperature, hydrogen can permeate steel. Such interaction can happen during manufacturing, assembly, or while the metal is in use — particularly when exposed to atomic or molecular hydrogen.

Where Does Hydrogen Come From?
- Manufacturing processes like acid pickling and electroplating can introduce hydrogen. For instance:
- Acid pickling, which removes oxide scales from steel surfaces, has hydrogen in its baths.
- During electroplating, used for depositing protective coatings like zinc, hydrogen gets generated on the metal's surface.

Risks During Service:
- Metals can absorb hydrogen when exposed to acids or due to corrosion during their service life.

How Does Hydrogen Cause Damage?
- Picture intergranular cracking: cracks forming and expanding along a metal’s weakened grain boundaries. With hydrogen embrittlement, hydrogen accumulates at these grain boundaries, further weakening the metal.

Three Key Factors for Hydrogen Embrittlement Failures:
- Stay tuned as we delve into the essential requirements that lead to failures attributed to this phenomenon.

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There are three requirements for failure due to hydrogen embrittlement:

A susceptible material.
Exposure to an environment that contains hydrogen.
The presence of tensile stress on the component.

High-strength steels with tensile strength greater than about 145 ksi (1000 MPa) are vulnerable to hydrogen embrittlement.

Exposure to hydrogen occurs during surface finishing process steps such as acid pickling and electroplating and during service if the steel is exposed to acids or if corrosion occurs.

As for the stress to cause fracture, even tensile residual stress within a component can be sufficient to cause failure of an embrittled material.

Steps that can be taken to avoid hydrogen embrittlement include reducing hydrogen exposure and baking after electroplating or other processes that lead to hydrogen absorption. Hydrogen embrittlement of electroplated components can be prevented by baking them within a few hours after the electroplating process. During baking, the hydrogen diffuses out of the metal.

For applications where there will be hydrogen absorption while a component is in service, the use of lower strength steels and reduction of residual and applied stress are ways to avoid fracture due to hydrogen embrittlement.

Finally, there are tests that can be performed to evaluate whether processing leads to steel hydrogen embrittlement. Here are two such tests:

ASTM F1940 Standard Test Method for Process Control Verification to Prevent Hydrogen Embrittlement in Plated or Coated Fasteners
ASTM F519 Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating Processes and Service Environments