## 3 Results and Discussion
Analysis of the polarization resistance \(R_{\text{P}}\), the rate of corrosion, and the protection level (Table 2) demonstrate that the protective effect of all the studied 3-mercaptoethanolalkyl derivatives of 5-amino-1\(H\)-1,2,4-triazole depends on their concentration and reaches its maximum when \(C_{\text{inh}}\geq 0.10\) mM. In the latter case \(R_{\text{P}}\) increases by over 100 times and the corrosion rate deteriorates correspondingly. When the concentration of the additive is 0.01 mM, inhibitor A does not demonstrate any protective effect, while inhibitors B and C slow down the rate of corrosion by two, and six times, respectively. Thus, even when the concentration is low, the protective effect of the inhibitor increases as the alkyl chain gets longer. The same results were obtained during the salt spray testing (Table 3). Figure 1: Anodic (1-4) and cathodic (1\({}^{\prime}\)-4\({}^{\prime}\)) polarization curves of \(\alpha\)-brass in a borate buffer (pH 7.4) with 0.01 M NaCl and 3-mercaptoethanolpropyl-5-amino-1\(H\)-1,2,4-triazole (**a**), 3-mercaptoethanolbutyl-5-amino-1\(H\)-1,2,4-triazole (**b**) and 3-mercaptoethanol(3-methylbutyl)-5-amino-1\(H\)-1,2,4-triazole (**c**) at the following concentrations: 1,1\({}^{\prime}\)\(-\)0; 2,2\({}^{\prime}\)–0.01 mM; 3,3\({}^{\prime}\)–0.10 mM; 4,4\({}^{\prime}\)–1.00 mM. Indeed, the period when the first signs of corrosion attack appear \(\tau_{\rm corr}\), if \(C_{\rm inh}\) = 10 mM, is shorter for inhibitor A, and longer for inhibitors B and C. With lower \(C_{\rm inh}\), 3-mercapobutyl-5-amino-1\(H\)-1,2,4-triazole demonstrates the best protective effect. \(\tau_{\rm corr}\) increases with higher \(C_{\rm inh}\), and reaches 6-12 days at 10 mM, which proves the effectiveness of 3-mercapoalkyl derivatives of 5-amino-1\(H\)-1,2,4-triazole for \(\alpha\)-brass in moist atmosphere. Another proof are the images of the surface of brass samples held in the salt spray cabin (Figure 2). They show that in the presence of the inhibitor the brass electrode remains bright and smooth even if the concentration of the organic additive is minimal. Without the inhibitors, the surface of the electrode darkens, and corrosion spots appear. To explain the effect, we carried out scanning electron microscopy and analyzed the micrographs of the brass electrode surface taken before, and after, the potentio-dynamic anodic polarization in a neutral chloride solution (Figure 3). Polarization was performed at intervals from the current-less potential to the activation potential. Figure 3 demonstrates that, without the inhibitors, multiple corrosion spots of about 10 \(\upmu\)m appear on the surface. However, when the brass is polarized in the solution with 1 mM of 3-mercapo(3-methylbutyl)-5-amino-1\(H\)-1,2,4-triazole, no pits can be observed on the surface. The micrographs show only scratches left from polishing the electrode. The results of the analysis of the elemental composition of the surface layer of the brass electrode before and after anodic polarization are given in Table 4.  
It is interesting that anodic polarization does not result in any change in the ratio of the atomic fractions of copper and zinc, which means that there is no dezincification. It is possible that oxides are formed during the anodic oxidation of both components of the alloy. This is also demonstrated by the presence of oxygen. The increase in the oxygen concentration on the brass surface in the presence of the inhibitor is observed because of the formation of a multicomponent passive film, which includes ZnO-xH\({}_{2}\)O, Cu\({}_{2}\)O, and CuO oxides [5; 14; 15; 16], together with sparingly soluble complex compounds of zinc and copper with molecules of the studied inhibitors [67; 68; 69]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Inhibitor**} & \multicolumn{4}{c}{\(C_{\rm inh}\), **mM**} \\ \cline{2-5}  & **0.0** & **1.0** & **5.0** & **10.0** \\ \hline A & & 68 & 98 & 152 \\ B & 3 & 173 & 194 & 212 \\ C & & 94 & 117 & 283 \\ \hline \hline \end{tabular}
\end{table}