Modeling of Anaerobic Corrosion Influenced by Sulfate-Reducing Bacteria

A laboratory experiment was conducted to investigate the corrosion influenced by sulfate-reducing bacteria (SRB). A mathematical model was developed and fitted to the pitting depths measured at 0.1 and 0.5 mM sulfate concentrations. The model was successful in predicting the pitting depth at two different sulfate concentrations when the kinetic variables reported in the literature were used. The deepest pitting depths were observed to be approximately 0.19 and 0.39 mm for bulk sulfate concentrations of 0.1 and 0.5 mM after 150 days of exposure, respectively. The pitting depths were predicted to be 0.17 and 0.36 mm for bulk sulfate concentrations of 0.1 and 0.5 mM after 150 days of simulation, respectively. The steady-state pitting depth was predicted to be 0.48 mm for a bulk sulfate concentration of 0.5 mM after 400 days of simulation. The model was most sensitive to the sulfate diffusion coefficient (${\rm D}_{{\rm SO}_{4}^{2-}}$), closely followed by the maximum sulfate utilization rate (q), and the biomass concentration ($X_{c}$), but it was less sensitive to the half-velocity coefficient ($K_{m}$). At the initial stage, the pitting depth was affected only by q and$X_{c}$. As the pitting depth increased, however, the diffusion of sulfate in the reaction zone became one of the dominant limiting factors. The decrease in the q or$X_{c}$value by 20% resulted in the increase in the pitting depth by 19%.