Oil Country Tubular Goods (OCTG) high strength steels are susceptible to hydrogen assisted cracking (HAC) due to hydrogen ingress as a result of exposure to environmental conditions (cathodic protection (CP) and/or H2S environments) and as such are prone to failure. In order to address the potential cracking susceptibility, a study was performed to understand fundamental parameters such as steady state hydrogen permeation flux, hydrogen concentrations and hydrogen trap binding energies of the high strength steel under charging conditions. Electrochemical permeation testing was performed on unstressed and 80%AYS stressed C110 pipe steel using an applied charging current density of 0.5 mA/cm2 in a 0.5M H2SO4 test solution at 75 F. Comparisons between the stressed and unstressed samples showed that there were no significant differences in steady state flux (Jss) and calculated hydrogen concentration for this charging condition. Further testing was performed to measure hydrogen uptake and time to saturation under the same charging conditions using the Silicone Oil Method. Subsequent laser thermal desorption mass spectrometry (LTDMS) was performed at the saturation point and at several temperature scan rates in order to calculate the apparent activation energy for hydrogen desorption, from which the binding energy for trap sites can be inferred (Eb).

Subject
Test methods, Materials, Fluxes, Binding energy, Hydrogen concentration, Activation energy, Desorption, Cathodic charging, Permeation, Stress, Steel, Hydrogen, Samples
Keywords:
High Strength Steels, Electrochemical Permeation Testing, Hydrogen Assisted Cracking, CP environment
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2019
Association for Materials Protection and Performance (AMPP)
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