## 1 Introduction  
Due to their high thermal conductivity, workability, and low cost, copper and copper-based alloys are widely used in heat-exchange equipment. Brasses, which are alloys of copper and zinc, are relatively harder and stronger, but are prone to corrosion in aggressive environments. Apart from the uniform attack, the most common forms of brass corrosion are selective leaching (dezincification) [1], stress-corrosion cracking [2; 3], and pitting. Selective leaching goes significantly faster in hydrochloric acid solutions, the rate of dezincification increases at higher temperatures [4]. In neutral chloride solutions, selective leaching occurs during the early stages of the corrosion process [5]. Corrosion models [6] demonstrate that, during selective leaching in brasses, zinc anodically dissolves, and as a result, vacancies and copper adatoms appear on the surface of the alloy. By means of surface diffusion, they form a highly developed phase characterised by the increased thermodynamic activity of copper [7]. Consequently, the corrosion of brasses becomes pseudo-selective, as both components are ionized followed by the deposition of copper [8; 9; 10]. As opposed to brass corrosion in an acidic environment,when the ionization/deposition results in the formation of a sponge Cu-metal, neutral chloride solutions produce additional multiple surface layers containing oxides of zinc and copper [11; 12; 13]. According to [5; 14; 15; 16], the formation of such layers from ZnO xH\({}_{2}\)O, Cu\({}_{2}\)O, and CuO passivate the surface of \(\alpha\)- and \(\beta\)-brasses in buffer chloride solutions and promotes corrosion resistance. According to [17], the sublayer resulting from dezincification is rich in corrosion-resistant copper, which also contributes to the protective effect. This sublayer, however, appears due to the sparingly soluble multicomponent structure formed when alloys are kept in alkali-chloride solutions for a long time. It is this structure that effectively protects the material from corrosion attacks when the concentration of chloride ions is relatively low, with CuCl providing additional protection [18]. When the chloride concentration reaches a certain critical point, the rate of corrosion increases dramatically due to the formation of soluble CuCl\({}_{2}\)- and discontinuity of the passive film. Compared to pure copper, brasses are much more prone to pitting, as the multicomponent surface layer containing ZnO is less resistant to dissolution in a corrosive environment [14; 15]. In the presence of chloride ions, dezincification and localized attacks on the surface of \(\alpha\)-brass take place simultaneously [19], which adds to the corrosive effect. Authors [1] suggests deoxygenation of solutions, anodic protection, and doping as methods of protection of brasses from selective leaching. These methods, however, have a number of drawbacks. Namely, they require constantly low concentrations of dissolved oxygen, additional sacrificial materials, or changing the composition of the copper-zinc alloy. These obstacles can be avoided by using inhibitors, which is quite a common technique to control corrosion of copper and its alloys in water solutions [20; 21; 22; 23]. The protective effect is found in organic compounds containing heteroatoms of nitrogen, sulphur, phosphorus, and oxygen, polar groups, heterocycles, and benzene rings with delocalized \(\pi\)-electrons [24; 25; 26; 27; 28; 29]. There are quite a number of substances that produce an anti-corrosion effect on brasses. Thus, quinoline derivatives are effectively adsorbed on \(\alpha\)-brass in an acid environment [30], while aminopropanol derivatives do so in neutral chloride solutions [31]. Diphenylamine derivatives form thin protective films [32], and phenol derivatives produce self-organizing layers on copper-zinc alloys [33]. However, the most effective corrosion inhibitors proved to be derivatives of azoles, widely used to control corrosion of copper, the main component of brasses [34; 35; 36; 37; 38; 39; 40].