aseous hydrogen weakens the mechanical strength of cast iron. this phenomenon often occurs in cast iron pressure vessels containing 100% gas hydrogen. H2 gas dissolves in metallic iron and diffuses into solid non-porous iron by an interstitial diffusion mechanism. H2 gas does not need to penetrate far into the iron to have a negative effect on the mechanical strength of iron. In the present situation, 100% of H2 gas at 1.0 atm and 100°C is contained within a 1.0 m internal diameter and wall thickness of 2.0 cm. The solubility of hydrogen in iron in 100°C is 2.2x10-7 mol of H/g Fe atoms. The diffusion coefficient of atoms of hydrogen in solid iron is 124.0x10-9 cm2 /sec at 100°C. Initially, there are no H atoms in solid iron. How many hours will it take for the hydrogen level inside the iron metal reaches 1.76x10-7 mol H atoms/g Fe at a depth of 0.1 cm from the surface exposed to hydrogen gas?
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