Numerical study on stress corrosion of X70 pipeline with the combined action of pits by sulfate-reducing bacteria and constant load

Abstract

The stress corrosion of pipeline steel was promoted by sulfate-reducing bacteria (SRB). However, the mechanism of SRB promoting stress corrosion is not clear. In this study, the effects of constant load, geometrical parameters and multi-pitting on stress corrosion in sea mud simulated solution were explored by establishing a 3D multi-physical finite element model to reveal the mechanism of SRB promoting stress corrosion. The results show that micron-sized pitting can cause significant local stress concentration. Pitting with similar geometries has little effect on maximum anodic current density. When the multiple pits are vertically distributed, the corrosion in the middle area of the two pitting increases. SRB-induced pitting causes stress concentration and tiny galvanic corrosion with the action of mechano-electrochemical effect, which make the pitting more likely to develop into micro-cracks in depth direction.

Keywords

• Carbon steel
• Stress corrosion
• Pitting
• Sulfate-reducing bacteria
• Constant load