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 (SAW) process. Three different temperatures were used: room temperature (25°C), 37°C, and 50°C. The corrosion rate, taken as the corrosion current density, I_corr, the amount of hydrogen uptake for the weldments, C₀, and the SSC susceptibility increased with an increase in the temperature from 25°C to 50°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.