Which statement best describes hydrogen embrittlement and materials at risk?

• A. Hydrogen embrittlement only occurs in non-metals
• B. Hydrogen embrittlement affects all metals equally
• C. Hydrogen embrittlement only occurs in non-metallic materials
• D. Ductility loss due to hydrogen in metal lattices; high-strength steels and some stainless and nickel-based alloys are at risk

Answer: (D)

Hydrogen embrittlement happens when hydrogen atoms diffuse into a metal lattice and weaken the metal’s bonding, especially at defects like grain boundaries and dislocations. Under stress, these weakened regions become initiation points for cracks, and crack growth can proceed rapidly, causing a loss of ductility and sometimes sudden fracture. The tendency to embrittle varies with material type and microstructure: high-strength steels and some stainless and nickel-based alloys are particularly vulnerable because their tightly bonded, strong lattices provide more favorable sites for hydrogen to accumulate and interact with the metal under load.

That’s why the statement describing ductility loss due to hydrogen in metal lattices and identifying high-strength steels and some stainless and nickel-based alloys as at risk is the best fit. Non-metals don’t exhibit hydrogen embrittlement in the same way, and not all metals are equally susceptible—susceptibility depends on strength, composition, and microstructure, which is why the other options don’t capture the reality of the phenomenon.