Hydrogen Embrittlement of a Duplex Stainless Steel in Alkaline Sulfide Solution

The hydrogen embrittlement (HE) behavior of UNS S31803 (2205) duplex stainless steel (DSS) was evaluated in alkaline sulfide solution (pH 13.3). The cathodic polarization response was evaluated using standard electrochemical techniques. Microhardness was used to measure the change in hardness upon exposure to the solution at select cathodic potentials. The hydrogen microprint technique (HMT) was used to observe the hydrogen distribution on the sample surface. Slow strain rate testing (SSRT) was conducted to determine HE susceptibility under applied potential in the range from −1,500 mV vs. saturated calomel electrode (SCE) to the corrosion potential (E_CORR). The effect of applied cathodic polarization on the HE susceptibility was assessed as a function of the changes in percent reduction of area (% RA), percent elongation at failure (% el_f), and the time to failure (TTF). The fracture morphology was examined using scanning electron microscopy (SEM) equipped with an energy-dispersive spectrometer (EDS). The results indicate that an increase in the magnitude of the applied cathodic potential enhances the severity of HE below a thresh-old potential of −1,100 mV_SCE. Results show that DSS may become susceptible to HE in alkaline sulfide environments where a high hydrogen fugacity is encountered because of galvanic effects or applied cathodic polarization.