A mathematical model of the lead-acid battery is developed with due consideration for the corrosion process that occurs at the interface between the active material and grid material of the positive plate. Three different modeling approaches are used to incorporate the effect of corrosion in the first-principles-based porous electrode model of the lead-acid cell. These approaches are used to examine the effects of corrosion during discharge, rest, and charge processes. First, the electronic conductivity of the positive plate is empirically expressed as a function of N, the number of cycles, next an current-resistance loss term to account for the increase in electronic resistance due to the formation and growth of passive corrosion layer is considered, and finally the corrosion phenomenon is incorporated as a side reaction occurring in the positive plate. It is identified that the modeling approach used in this work can be used to investigate the effect of corrosion on lead-acid battery performances. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3190510] All rights reserved.