Effects of biofilm development on corrosion behaviours of X80 pipeline steel in soil environment

In this work, the biofilm development behaviours of sulfate-reducing bacteria (SRB) on X80 pipeline steel in Guangzhou soil solution were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM). The effects of time-dependent biofilm on stress corrosion and electrochemical corrosion were studied by using electrochemical methods and surface characterisation. Results show that the corrosion rate and stress corrosion susceptibility are affected significantly by the biofilm state. The electrochemical measurements showed a dynamic corrosion rate change process, the R _t increased from 13410 to 13540 Ω·cm ⁻² , then decreased to 4707 Ω·cm ⁻² , and finally rebounded to 10890 Ω·cm ⁻² with the development of biofilm. Stress corrosion susceptibility followed the order 5d < 1d < 2d < 4d < 3d, consistent with the biofilm growth stages. Anodic dissolution was the dominant corrosion mechanism, and the mature biofilm effectively suppressed localised corrosion and stress cracking by hindering ion and electron transfer. These findings elucidate the dynamic role of SRB biofilms in modulating pipeline steel corrosion and provide valuable guidance for microbial corrosion control in buried pipelines.