The hydrogen uptake behavior of ASTM A 516 grade 70/grade 60 (UNS K02700 / UNS K02100) steels was studied in near neutral and high pH solutions representing aqueous alkanolamine/sulfolane* solutions used in gas sweetening operations (removal of hydrogen sulfide and carbon dioxide). Since known test techniques for hydrogen charging activities did not reveal sufficient sensitivity for hydrogen uptake a unique modification of fracture mechanics J-integral testing methodology was employed. The tests were complemented with slow-strain-rate-testing. In contact with high pH solutions the steels investigated showed only minor hydrogen uptake without a high potential for hydrogen induced cracking (HIC) formation. However, when in contact to lower pH solutions (pH below 7.1) hydrogen uptake was significant and HIC can develop at non-metallic inclusions. It was also concluded, typical service conditions for aqueous alkanolamine/sulfolane solutions do not impose a severe risk for HIC. Modern HIC resistant steels tend to degrade by HIC at a much lower pH than considered in this study for aqueous alkanolamine/sulfolane solutions.
Key Words hydrogen induced cracking, gas sweetening, alkanolamine/sulfolane, J-integral test technique, acid gas, hydrogen sulfide removal