Which type of environmental cracking is hydrogen induced cracking (HIC)?

• A. Hydrogen induced cracking (HIC)
• B. Pitting corrosion
• C. Erosion
• D. Uniform corrosion

Answer: (A)

Hydrogen-induced cracking is a form of hydrogen embrittlement, where hydrogen atoms diffuse into the metal and reduce its cohesive strength, allowing cracks to form and propagate under tensile stress in a hydrogen-rich environment. This mechanism is distinct from other forms of environmental attack: pitting corrosion is localized metal loss from breakdown of the protective film, erosion is wear caused by fluid flow removing material, and uniform corrosion is even, general thinning from chemical attack. In practice, hydrogen-induced cracking tends to occur in high-strength steels exposed to hydrogen-containing media (such as sour environments), especially where residual or applied stresses are present, and it can be mitigated by reducing hydrogen entry and controlling stresses.