Seawater is a corrosive medium that adversely affects the numerous metallic constructions used in construction and industry and thus causes significant economic damage and pollutes the environment. Despite the fact that corrosion resistant alloys such as stainless steel and copper and nickel alloys are often used in the marine environment, which are characterized by the possibility of spontaneous formation of a protective layer of oxide on a metal surface, it is desirable to use some type of protection to extend the life of the structure. In closed systems, corrosion inhibitors, substances of inorganic or organic origin are often used which, when added in small quantities to an aggressive medium, can greatly reduce the corrosion rate of metal. Their efficacy depends on the type of inhibitor, the medium to which the inhibitor is added, the temperature and concentration. Organic inhibitors are adsorb on the metal surface or combine with corrosion products on the surface while forming a protective layer, mainly due to the presence of polar functional groups in the molecular structure. Among the most effective inhibitors of corrosion of copper alloys are those containing heteroatoms such as sulfur, nitrogen, oxygen and phosphorus. One of the major organic corrosion inhibitors used to protect copper and its alloys is benzotriazole (BTA)1, a nitrogen heterocyclic compound. In addition to benzotriazole, the efficacy of numerous other organic inhibitors, such as derivatives of imidazoles, triazoles, amines and amino acids.2,3 Most commercial inhibitors, like benzotriazole, are not ecologically acceptable, so new ecologically acceptable compounds are being investigated. The aim of this work was to examine and compare the efficacy of Cu-Ni alloy protection by various benzimidazole derivatives (2-amino-5(6)-nitrobenzimidazole, 2-amino-5-(6-cyanobenzimidazole, 2-aminobenzimidazole, 2-amino-6)-(2-imidazolinyl) benzimidazole hydrochloride) in artificial seawater (3 % NaCl solution). The corrosion rate was determined by Tafel's extrapolation method, which showed that the most effective inhibitor is 2-amino-5 (6) -nitrobenzimidazole at a concentration of 10^-3M exhibits an inhibitory effect of 71 %. Then the electrochemical tests were performed in time for the two most effective inhibitors (linear polarization method and electrochemical impedance spectroscopy (EIS) method.) The surface of the samples was analyzed by scanning electron microscopy and spectroscopic FTIR. It was concluded that the efficacy of the inhibitor increases with prolonged exposure to the inhibitor solutions as well as with increase of inhibitor concentrations.