First principles thermodynamic modeling of aqueous lead corrosion*

The corrosion of lead water pipes is a major public health concern. Treatment strategies aim to induce passivation, the formation of a protective solid layer between the pipe and the water. While prevention of lead corrosion is understood from engineering practices, computational models using decades old data remain unable to accurately predict the behavior of real pipes using thermodynamics alone. Here we calculate free energies of formation for solid lead compounds with density functional theory (DFT) and construct electrochemical phase diagrams for various water conditions. We find that the Perdew-Burke-Ernzerhof revised for solids (PBEsol) functional with spin-orbit coupling is the best choice for this Pb-H2O system. Our phase diagrams predict the corrosion of lead in standard state water conditions, confirming the need for corrosion inhibitors. We find that lead carbonates form in broad water conditions. However, our model did not find stable lead phosphates, contrary to the historical success of orthophosphate treatments, indicating the need for further investigation. Our work demonstrates the potential for computational materials physics techniques to provide insight into the thermodynamics of lead corrosion.