Hydrogen Sulfide Stress Corrosion Cracking of High Strength Steel Wire

High strength (244,000 psi ultimate tensile strength) cold drawn carbon steel wire is susceptible to cracking in hydrogen sulfide solutions at room temperature at stress levels less than 15% of the ultimate strength. Failure occurs with an unusual tendency for cracks to form at 45 degrees to the direction of tensile stress. Time to failure is decreased by cathodic polarization and is increased by anodic polarization. Susceptibility reaches a maximum at near room temperature and decreases at both lower and higher temperature. These facts are consistent with a hydrogen embrittlement mechanism of failure. The buildup of large pressures of molecular hydrogen within hollow steel cylinders exposed to H₂S solutions is found to be much greater at the higher temperatures at which cracking susceptibility abates. The latter observation is contrary to the predictions of a mechanism of hydrogen embrittlement based on molecular hydrogen pressure but it is shown to be consistent with those of an internal adsorption mechanism.