Modelling mass transport in aqueous CO2 corrosion in turbulent pipe flow

A predictive model is described to simulate the aqueous CO2 corrosion of iron in turbulent pipe flow under both developing and fully developed mass transport conditions. The mass transfer is modelled with a two-dimensional LRN κ-ε turbulence model which simultaneously solves the conservation equations for mass, momentum, kinetic energy of turbulence and its dissipation rate, along with the concentrations of various dissolved species. The model takes into account the slow homogeneous chemical reaction of CO2 hydration by the inclusion of extra source terms in the transport equation for H2CO3. Other homogeneous reactions are assumed to be in equilibrium with the equilibrium adjusted after each iteration. The cathodic reactions considered are the reduction of H2CO3 and H+. The anodic reaction is the iron dissolution. Concentration profiles for various species under different conditions are obtained. Corrosion rates are calculated based on the mixed potential theory. The effect of the slow homogeneous chemical reaction of CO2 hydration on the developing mass transfer boundary layers is also investigated. (orig.)