Study on porous layer formation kinetics under CO2‐aqueous conditions via partial‐bounceback lattice Boltzmann method

Abstract

AbstractThe porous layer of FeCO3, as a main corrosion product in CO2 aqueous environments, has a critical influence on corrosion kinetics. However, multi‐physicochemical processes are involved in the evolution of the FeCO3 porous layer, such as homogeneous chemical reactions, multi‐component transport, and dissolution/precipitation at the solid–fluid interface, which is notoriously complicated to be totally understood. This study builds a numerical framework based on partial‐bounceback lattice Boltzmann method to investigate the reactive transport in the evolving porous layer. Experimental observations on polarization behavior confirm the model performance. Results show that the formation of a protective FeCO3 film is self‐promoted under anodic polarization in CO2‐saturated alkaline solutions and the “self‐promoted” effect is highly associated with local water chemistry at the interface. The interfacial FeCO3 supersaturation is several orders of magnitude higher than that of the bulk, while the interfacial concentrations of CO32− and HCO3− are slightly changed from bulk. The growing porous layer hinders Fe2+ from transporting away from the interface, promotes the precipitation of FeCO3, and further facilitates a denser film to inhibit anodic processes, which is another manifestation of the self‐promoted effect.