## 2 Materials and Methods  
Electrochemical measurements were performed at room temperature (\(\sim\)25 \({}^{\circ}\)C) on brass (Cu/Zn: 63/37) electrodes in an unstirred borate buffer water solution (pH 7.4) with natural aeration, in the presence of the inhibitor and 10 mM NaCl. A classical electrolytic three-electrode cell with unseparated electrode spaces was used in order to accelerate transient measurements. Derivatives of 5-amino-1\(H\)-1,2,4-triazoleole synthesised at Voronezh State University were used. Their names, structures, and solubility in water are given in Table 1.  
The saturated silver chloride reference electrode was placed in a separate container connected to the electrolytic cell by an agar-agar based salt bridge and filled with potassium nitrate saturated solution. The auxiliary electrode was a platinum grid. The working brass electrode was polished by K3000 sandpaper, degressed in 96% ethanol, and washed with distilled water. The potentials of the working electrode (\(E\)) are given according to the standard hydrogen electrode (SHE) scale. The current density \(i\) was calculated by dividing the actual current \(I\) by the geometric area of the working electrode (2.25 cm\({}^{2}\)). Electrochemical measurements were performed using IPC-PRO potentiostat. In order to remove the oxide film appearing in air, the working Cu-electrode was polarized at \(E=-0.60\) V for 15 min prior to the experiment. The electrode was then held in the solution for about 3 to 5 min until the stable free corrosion potential (\(E_{\text{corr}}\)) established. The working solution was then mixed with an NaCl solution while stirring, so that the concentration of chloride ions would be \(C_{\text{Cl}}{}^{-}=10\) mM. The studied inhibitors were also added to the solution in the concentration of \(C_{\text{inh}}=0.01\), \(0.10\), and \(1.00\) mM. After the new \(E_{\text{corr}}\) value was established, the \(I,E\) polarization curve was registered by scanning the potential towards either the anodic or the cathodic direction at 0.2 mV/s. Fitting potential (\(E_{\text{pit}}\)) was identified by the rapid increase in the current on the anodic polarization curve. Pits were then visually identified on the surface of the electrode. The measurement error for \(E_{\text{pit}}\) was below 0.03 V.  
The rate of corrosion in current units (\(i_{\text{corr}}\)) was determined by the polarization resistance technique as summarized by [PERSON] [70; 71]. The polarization curve was previously registered by scanning the potential from \(E=E_{\text{corr}}-0.03\) V to \(E=E_{\text{corr}}+0.03\) V at 0.2 mV/s. The polarization resistance \(R_{\text{p}}\) was \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Symbol** & **Name** & **Formula** & **Solubility** \\ \hline A & 3-mercaptoethanolpropyl-5-amino-1\(H\)-1,2,4-triazoleole & & \\ B & 3-mercaptoethanolbutyl-5-amino-1\(H\)-1,2,4-triazoleole & & \\ C & 3-mercapto(3-methylbutyl)-5-amino-1\(H\)-1,2,4-triazoleole & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Inhibitor names, structures and solubility in water. then calculated as the slope of the polarization curve, replotted in \(\Delta E\),\(i\)-coordinates (\(\Delta E=E-E_{\text{corr}}\)), at \(E_{\text{corr}}\). The polarization curve was then plotted in coordinates 2.3\(\cdot R_{\text{P}}\cdot i-\Delta E\), and the Tafel slopes of the half-reaction on the anode \(b_{a}\) and the cathode \(b_{c}\) were determined by means of the TableCurve software as the approximation parameter of the equation 2.3\(\cdot R_{\text{P}}\cdot i=\frac{b_{a}\cdot b_{c}}{b_{a}+b_{c}}\left[\exp \left(\frac{\Delta E}{b_{a}^{2}}\right)-\exp\left(\frac{\Delta E}{b_{c}^{2}} \right)\right]\), which at \(\Delta E=0\) gives \(i_{\text{corr}}\). The measurements were performed at least 5 times for each of the studied concentrations of the inhibitor until the reproducible data was obtained. The data was then statistically analysed.