Hydrogen diffusion and trapping in nickel-based alloy 625: An electrochemical permeation study

This work studied the effect of cathodic charging conditions on hydrogen diffusion and trapping behavior in a nickel-based Alloy 625 using the electrochemical permeation approach. Results showed that the effective diffusion coefficient of hydrogen can be expressed as Deff=1.82×10−7exp(−44.46kJmolRT)m2/s. A sinusoidal trend in Deff with charging current density was observed showing a deflection point at -40 mA/cm2, which contributes to the most efficient hydrogen permeation. In addition, the thermodynamic relationship between hydrogen activity and electrochemical potential was investigated. Furthermore, the energy associated with the solubility energy of interstitial hydrogen and reversible trapping site was determined as 9.90 kJ/mol and 26.04 kJ/mol, respectively.