The corrosion inhibition behavior of benzotriazole (BTA), Na3PO4 (SP) and their mixture on zinc in 17 wt% (0.534 mol l-1) tetra-n-butylammonium bromide aqueous solution was investigated by weight-loss test, potentiodynamic (Tafel) polarization measurement, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. After addition of inhibitor(s) into the TBAB aqueous solution the corrosion current density decreased and the charge transfer resistance increased, indicating that BTA or Na3PO4 or inhibitor mixture could protect zinc in aqueous TBAB solution. It was observed that the synergistic protection effect of BTA and Na3PO4 was evident. The formulation consisting of 0.1 g l-1 BTA and 1 g l-1 Na3PO4 had more than 93% corrosion inhibition efficiency calculated according to different methodologies. The main function of Na3PO4 seems to form the thin layer consisting of ZnO, Zn(OH)2 and Zn3(PO4)2, whereas BTA can stabilize this layer by incorporation into it or/and adsorption on it so that corrosion inhibition occurs after immersion of zinc into the solution containing both inhibitors.