Fracture mechanics of carbon steel under different carbon monoxide and dioxide gas mixture conditions in water

Abstract

The results of carbon steel stress-corrosion cracking experiments in a CO-CO2-H2O environment at varying gas mixtures are presented. The fracture mechanics of carbon steel were investigated in distilled water under CO-CO2 combinations of various compositions. For each mixture, the subcritical rates of crack propagation and thresholds for stress intensity were established. Using an applied electrochemical potential, the effects of cathodic and anodic polarization on carbon steel were examined. At a low-stress intensity threshold of 3 MPa√m, cracking was caused in a 50% gas mixture. The stress intensity threshold was double that of the 50%CO. Low dissolved oxygen content was reported at 1% CO, with a threshold of 15 MPa√m. As a result, increasing CO had the opposite effect on the stress intensity threshold. Cathodic polarization reduced the susceptibility to cracking and the growth rates of subcritical cracks ranged from 10−10 to 10−9 ms−1. The underpinning stress corrosion mechanisms are investigated further, as well as their consequences in different CO-CO2-H2O environments.

Keywords

• Stress-corrosion cracking
• Carbon steel
• Carbon monoxide
• Carbon dioxide
• Fracture mechanics
• Crack growth rate