The review is mainly concerned with synergistic effect of corrosion inhibitors in aqueous solutions. The following factors influencing the combined action of inhibitors are reviewed: charge sign of the metal
surface to be protected; nature of the electrochemical reactions causing the corrosion of a metal; ability of inhibitors to form complexes with metal cations; and peculiarities of chemical structure of inhibitom. Keywords: adsorption, acid, complexes, corrosion inhibitor, potential, synergistic effect.