During the process of electro-dehydration, the electric field strength should be set below a critical value (E-crit) to inhibit droplet-interface partial coalescence. The alkali present in alkaline-surfactant-polymer flooding may affect E-crit because they change the electrical properties of produced liquids. In view of this, this study investigated the effects of Na2CO3 solution concentration, electric field waveform, and frequency on the root mean square (RMS) values of E-crit. The results show that elevated Na2CO3 concentrations increase E-crit, owing to the enhanced solution conductivity which may affect the charge transfer during coalescence. The convection of ions is associated with penetration of fluid into the bulk phase and an increase in Na2CO3 concentration decreases the penetration velocity. Moreover, increasing the AC or pulsed electric field frequency can increase E-crit, and the optimal waveform (i.e., with the largest E-crit) varies with frequency. These findings will be useful for optimizing electro-coalescence systems. (C) 2019 Elsevier Ltd. All rights reserved.