Susceptibility of Conventional Pressure Vessel Steel to Hydrogen-Induced Cracking and Stress-Oriented Hydrogen-Induced Cracking in Hydrogen Sulfide-Containing Diglycolamine Solutions Available to Purchase

Hydrogen-induced cracking (HIC) and stress-oriented hydrogen-induced cracking (SOHIC) tests were conducted on a conventional type A516-70 (UNS K02700) pressure vessel steel exposed to hydrogen sulfide (H₂S)-containing diglycolamine (DGA) gas-sweetening environments. Base-line HIC and SOHIC tests were conducted in NACE TM0284-96 Solution A. For the SOHIC tests, four-point double-beam specimens were stressed to 60%, 80%, or 100% of the yield strength of the steel to study the effect of applied stress. Test conditions included solutions containing 70 wt% DGA and 500 ppm H₂S to ≥ 0.45 M-H₂S/M-DGA and temperatures of 25°C, 45°C, and 80°C. Corrosion rates of the steel were calculated from weight loss of the HIC specimens to compare the severity of the test environment with the actual service environment. Cracks were characterized in terms of crack length ratio (CLR), crack thickness ratio (CTR), and crack sensitivity ratio (CSR). Results indicated that conventional type A516-70 pressure vessel steel was not susceptible to HIC or SOHIC in various H₂S-containing DGA solutions at the temperatures studied.