Gaseous hydrogen permeation in X65 D pipeline steel and a preliminary evaluation of the influence of oxygen

The dissolution of gaseous hydrogen into pipeline steel has been previously shown to be influenced by the presence of oxygen in the hydrogen gas. This study reports on hydrogen permeation experiments using vintage X65 D pipeline steel extracted from the Dampier Bunbury Natural Gas Transmission Pipeline. The aim was to quantify the effect of oxygen on hydrogen permeation. A gas-phase permeation apparatus was designed and built. A permeation model incorporating the appropriate boundary conditions was derived. The hydrogen concentration dissolved in the X65 D using pure hydrogen in these experiments was considerably lower than previously reported. The first set of permeation experiments with hydrogen gas containing oxygen found no effect of oxygen on hydrogen permeation (for oxygen concentrations of 100, 300 and 1000 ppm) with a hydrogen pressure of 81 bar. The second set of permeation experiments found a slight effect of oxygen (for oxygen concentrations of 100, 5000 and 12000 ppm) with a hydrogen pressure of 94 bar. The steady-state hydrogen permeation flux slowly recovered to the value measured in pure hydrogen. This indicated that preadsorbed oxygen initially impeded hydrogen uptake and dissolution in the steel but was not an effective long-term measure to lower the hydrogen in solution in the X65 D under these conditions. • Hydrogen permeation in X65 D pipeline steel and the impact of added O 2 were investigated. • A gas-phase permeation apparatus was designed and built, and a model with suitable boundary conditions was derived. • With up to 1000 ppm O 2 , no effect on hydrogen permeation was found at 81 bar hydrogen partial pressure. • The addition of 100–12000 ppm O 2 decreased hydrogen permeation slightly at a hydrogen partial pressure of 94 bar. • The reduced hydrogen steady-state flux recovered to the level measured in pure hydrogen; there was no lasting effect.