Hydrogen accumulation and diffusion in cylindrical-shaped pipeline steels with coating defects

Abstract

The effective diffusion of hydrogen in a cylindrical geometry, mimicking a pipe with a coating defect, was investigated by modelling and verified experimentally. Analytical solutions for the extreme cases of no hydrogen uptake and constant hydrogen uptake were developed. Simulations showed less than 5% error, when compared to two well-documented reference cases for diffusion. The intermediate case of modelling kinetic controlled hydrogen uptake was investigated and the effects of time, position, effective diffusion coefficient, corrosion protection current density and their binary interactions, were reported. Modelling results show, that certain parameter combinations such as effective hydrogen diffusion coefficients between 10−11 - 10−9.5 m2 s−1, particularly in combination with a hydrogen uptake jH of more than 0.1 A m−2, may lead to locally increased hydrogen concentrations in the material.