Removing hydrogen in solid metal using electric current pulse

Abstract

Hydrogen in solid metals can cause accidental fracture of engineering alloys in service, and thus has become an important issue in industrial applications, such as power generation, hydrogen storage, petroleum transport and hydrocarbon extraction. Through experiments, it was found that the elimination rate of hydrogen atoms in high strength alloy was greatly accelerated, and the equilibrium hydrogen content in the samples was decreased to a quite low level. The electric current provided an additional free energy term for the alloy system based on the current density distribution. The electrical free energy tends to reduce the electrical resistance of the system. Meanwhile, hydrogen atoms in lattice and traps caused the local electrical conductivity changes, thereby changing the current distribution and bringing the free energy of the alloy system to a new state. In this case, the diffusion activation energy and the height of energy barrier for hydrogen trapping sites were decreased. As a result, the diffusion coefficient became larger and the irreversible hydrogen were decreased, so the content of diffusible hydrogen was increased, and the hydrogen removal was accelerated. In principle, the proposed treatment helps to remove hydrogen from solid metal to a rather low level to avoid further hydrogen-induced damages, and should work for majority of alloys especially the high strength alloys.