Enhancing the resistance of pipe joint to riboflavin mediated microbial corrosion via increasing heat input

This study investigated the dual role of heat input (HI) and riboflavin on microbiologically influenced corrosion (MIC) of pipe joint. The results showed that localized corrosion of the base metal (BM) and weld zone (WZ) was more severe than that in the heat affected zone (HAZ), but the general corrosion of the former two regions was less severe than that in the latter. The pit depths of BM (8.84–14.61 μm) and WZ (7.71–9.75 μm) were consistently significantly higher than that in HAZ (4.04–5.67 μm). Riboflavin accelerated corrosion via extracellular electron transfer (EET), increasing corrosion rate of BM by 46.8% (from 29.2 μm/y to 42.9 μm/y). The R⁻¹ values (3.59 × 10⁻³–1.01 × 10⁻² Ω⁻¹·cm⁻²) were generally higher than those of specimens in medium without riboflavin (2.67 × 10⁻³–8.19 × 10⁻³ Ω⁻¹·cm⁻²). However, higher HI effectively mitigated this acceleration by coarsening HAZ grains and reducing Widmanstätten structures. HI is a key parameter to optimize the welding process to improve MIC resistance, providing a new strategy for pipeline protection.