Abstract
In this paper, hydrogen absorption behavior into iron was investigated by measuring alternating current responses for hydrogen-entry side and hydrogen-withdrawal side in an electrochemical hydrogen permeation cell. Hydrogen absorption efficiency of iron was evaluated as a function of electrode potentials by using both DC and AC components of the current responses. The hydrogen absorption efficiency of iron increased with decreasing cathodic polarization. Furthermore, frequency response characteristics of the hydrogen absorption efficiency were investigated at various polarization potentials and the results indicated that the hydrogen absorption efficiency decreased with increasing frequency of the perturbation potential. The frequency response characteristics of the hydrogen absorption efficiency was also simulated by using Fick's second law and the results suggested that hydrogen absorption kinetics can be considered to be faster than diffusion of hydrogen atoms in iron and to be under an equilibrium condition. By analyzing AC responses for hydrogen-entry side and hydrogen-withdrawal side, hydrogen absorption behavior into iron can be successfully evaluated.
