Microalloyed pipeline steels have been developed for applications in hydrogen sulfide environments (sour environments), focusing on the required yield strength. Nevertheless, the cracking susceptibility is mainly affected by the microstructure produced during the manufacturing processes. In sour environments, most of the failures can be related to the susceptibility to hydrogen embrittlement for higher mechanical grades. However, sulfide failures in lower grade steels are related to the anodic dissolution. In this work, APi 5L X52 steels were evaluated in order to determine their cracking susceptibility in pressurized sour environments with brine solutions at 50°C, by using M-WOL specimens. The steels showed a marked corrosion in the surfaces exposed to the environments showing dissolution bulbs that may be related to slip-dissolution as the main mechanism in order to induce cracking.
Keywords: pipeline steels, microalloyed, slip-dissolution, hydrogen sulfide, oil, gas transport, sulfide stress corrosion.