API X70 pipeline steel was investigated with regard to hydrogen diffusion and fracture properties. The electrochemical permeation technique was used to study hydrogen diffusion properties, while in situ fracture mechanics testing was performed in order to establish the hydrogen-affected threshold stress intensity. The average effective room-temperature diffusion coefficient at was 7.60 x 10-11m2/s for the base metal, 4.01 x 10-11m2/s for weld metal and 1.26 x 10-11m2/s for the weld simulated heat affected zone. Hydrogen susceptibility was pronounced for the heat affected zone samples.

Hydrogen Diffusion and Hydrogen Influenced Critical Stress Intensity in an API X70 Pipeline Steel Welded Joint - Experiments and FE Simulations. V.Olden, A.Alvaro, O.M.Akselsen: International Journal of Hydrogen Energy, 2012, 37[15], 11474-86