Sulfide stress cracking susceptibility of welded X-60 and X-65 pipeline steels

The susceptibility of API X-60 and X-65 longitudinal weld beads to sulfide stress cracking (SSC) has been evaluated using slow strain rate tests (SSRT) in the NACE solution saturated with hydrogen sulfide (H2S). The tests were supplemented by potentiodynamic polarization curves and hydrogen permeation measurements. The weld beads were produced using the submerged arc welding (SAM) process. Three different temperatures were used: room temperature (25 degrees C), 37 degrees C, and 50 degrees C. The corrosion rate, taken as the corrosion current density, I-corr, the amount of hydrogen uptake for the weldments, C-0, and the SSC susceptibility increased with an increase in the temperature from 25 degrees C to 50 degrees C. Although anodic dissolution seems to play an important role in the cracking mechanism, the most likely mechanism for the cracking susceptibility of X-60 and X-65 weldments in H2S solutions seems to be hydrogen embrittlement.