There have been many attempts to measure the diffusivity and permeability of hydrogen
in the steel under tensile straining condition using the electrochemical hydrogen permeation
technique (HPT). However, the different experimental conditions relating to strain rate and
applied electrochemical parameters often lead to unrealistic data. In this work API(1) X65 grade
linepipe steel having a high sulfide stress cracking (SSC) resistance was used and most
experimental conditions were determined according to the ISO170811 standard. NACE-A
solution was selected as the hydrogen charging solution according to the NACE procedure
TM0177A2. Applied stresses were smaller than threshold stress to avoid failure of the
specimen. In this study, the permeability, apparent diffusivity, apparent solubility of diffusible
hydrogen and the amount of irreversibly trapped hydrogen was measured by a modified HPT,
and were are correlated with the SSC resistance to investigate the role of hydrogen in causing
SSC.
Keywords: linepipe steel, sulfide stress cracking, electrochemical hydrogen permeation
technique, hydrogen trapping