How does hydrogen blistering occur?

Hydrogen blistering is a phenomenon that occurs when atomic hydrogen diffuses into the material and becomes trapped in voids or inclusions, leading to the formation of bubbles. This process typically happens in metals and alloys that have been exposed to hydrogen-rich environments, such as those found in chemical processing or during corrosion reactions.

When atomic hydrogen permeates the metal, it may accumulate at imperfections or voids within the material. As more hydrogen diffuses in, the pressure from the accumulating hydrogen may exceed the material's capacity to contain it, ultimately resulting in blister formation. These blisters can compromise the structural integrity of the metal, leading to failures such as cracking or spalling.

The other alternatives describe different issues related to materials but do not accurately represent the mechanism of hydrogen blistering. The loss of ductility primarily pertains to material properties under stress rather than hydrogen interaction. High temperatures and pressures can affect many aspects of material behavior, but they do not directly account for the specific mechanism of hydrogen blistering. Finally, galvanic action involves electrochemical reactions between different metals, which is unrelated to the diffusion and entrapment of hydrogen in materials.