Stress corrosion of HAZ subdivision of X80 pipeline steel in sterile high-sulfate soil

Abstract

The welding heat affected zone (HAZ) is a high-risk region of corrosion, and influenced by multi-factors, such as stress, microbe and microstructure. Sulfate reducing bacteria (SRB) enhance the corrosion of the stressed HAZs, especially coarse-grained HAZ (CGHAZ). CGHAZ has least percentage of HAGBs, largest effective grain size, and highest volume fraction of MA island, which leads to the severer corrosion. SRB accelerate the localized corrosion of steel HAZs, and the maximum pitting depths of CGHAZ with and without SRB reach 9.97 and 7.65 μm, respectively. The elastic stress lowers the equilibrium potential and weakens the protective ability of film, which boosts the corrosion process, while SRB further enhance this accelerating effect of the stress on the corrosion.

Keywords

• SRB induced corrosion
• Elastic stress
• X80 steel
• CGHAZ
• Saline soil