Localized corrosion and brittle fracture of X80 carbon steel under tensile stress induced by sulfate reducing bacteria

The microbiologically influenced corrosion (MIC) of X80 carbon steel under varying tensile stresses with the presence of sulfate reducing bacteria (SRB) was investigated. The stress loads affected the SRB sessile cell counts on the carbon steel, and exerted a significant influence on the rate of MIC to which the carbon steel was subjected. Stresses below 400 MPa elicited a modest promotion effect, whereas the stress of 550 MPa which was approaching the yield strength markedly expedited the corrosion of SRB on X80 carbon steel. Finite element simulation revealed that the elastic stress of 550 MPa led to plastic deformation in the stress concentration zone at the base of the corrosion pit, exacerbating the dissolution of the metal in pits and inducing secondary pitting corrosion. Additionally, this work confirmed that SRB promoted the permeation of hydrogen into the carbon steel matrix. The coexistence of high elastic stress and SRB rendered X80 carbon steel more prone to brittle fracture.