A generalized expression for the estimation of hydrogen diffusion and trapping parameters from permeation testing

Being a multifaceted phenomenon, hydrogen embrittlement can be influenced by the kinetics of hydrogen diffusion and its distribution within components, making diffusion modeling a valuable tool for understanding and managing embrittlement risk. The presence of hydrogen trapping complicates diffusion and therefore the interpretation of diffusion-related experiments such as permeation tests. Accordingly, numerous methods have been proposed to estimate trapping parameters from permeation data. Here, a general estimation formula is presented based on the work of McNabb and Foster. When applied to published permeation transient datasets, the resulting trapping parameters improve the curve reconstruction, reducing the modeling error from 11.8% to 1.7% in the best case and from 4.65% to 4.54% in the worst case. In addition, the formulation is generalized to include multiple trap types.