Exam Question

### Introduction to Hydrogen Damage
Hydrogen damage is a general term for the mechanical degradation of metals, primarily steels, caused by interaction with hydrogen. The fundamental mechanism involves the distinct behaviour of atomic versus molecular hydrogen. Atomic hydrogen (H), being extremely small, can readily diffuse into the metal's crystal lattice. Once inside, it can cause damage through several mechanisms. In contrast, molecular hydrogen (H₂), formed when two hydrogen atoms combine, is too large to diffuse through the lattice, leading to its entrapment and subsequent pressure build-up within the material's internal defects.
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### (a) Hydrogen Blistering