In this work, a mechanistic model of drop coalescence based upon a stochastic film-drainage analysis is developed. The coalescence model accounts for previously considered factors, such as turbulence intensity, drop size, and drop deformability, while additionally describing the dual effects of drop surface potential and system electrolyte concentration. Model results indicate that electrostatic repulsion may strongly inhibit small drop coalescence, as well as coalescence between larger deformable drops. Comparison of model predictions to data from several transient coalescence experiments shows good agreement in most cases.