# Investigation of CuTi Alloy for Applications as Non-Sparking Material
## 3 Results and Discussions
### Electrochemical Corrosion Resistance of CuTi Alloys
For the hot-rolled sample, chemical analysis revealed sodium-based compounds on the surface, as shown in Table 3.  
Considering the degree of oxidation (Table 3) and the general chemical composition, it was found that the cast sample exhibited a higher degree of oxidation. Copper (II) chloride, also known as cupric chloride, is an inorganic compound with the chemical formula CuCl\({}_{2}\). The cast sample, as shown in Figure 6a, contained more areas with a high concentration of precipitates and areas where no precipitates were present, while the rolled sample, shown in Figure 6b, had a uniform distribution of precipitates on the entire Cu matrix. Figure 5: Electro-chemical corrosion behavior (**a**) Tafel diagram and (**b**) cyclic potentiometry. Figure 6: Sample surfaces after electrochemical corrosion resistance testing and chemical analysis points: (**a**) cast and (**b**) rolled. From the results presented in Table 3, it can be observed that there are areas, e.g., point 1 on the rolled sample, where Ti is found in a higher percentage, probably due to the presence of TiCu-based compounds that have oxidized easily, but have not formed chlorine or sodium compounds or have not been covered by these compounds on the surface. The copper was actually dissolved out of the NaCl/O\({}_{2}\)/H\({}_{2}\)O solution. This is because oxygen oxidizes copper over an extended time, and NaCl lowers the electrochemical potential for this reaction (probably forming some complex chloride compounds such as [CuCl\({}_{2}\)]\({}^{-}\), [CuCl\({}_{4}\)]\({}^{2-}\), etc.). Theoretically, in the absence of oxygen, there would be no reaction. The greater the stability of the complexes, the lower the potential. Therefore, when the system finally \"chooses\" the most stable possible complex (here, CuCl\({}_{4}\)(\({}^{2-}\)), the potential for the reaction Cu\({}^{2+}\) + 4 Cl\({}^{-}\)\(\rightarrow\) CuCl\({}_{4}\)(\({}^{2-}\)) will be significantly lower than that of oxygen: O\({}_{2}\) + 4e\({}^{-}\) + 2H\({}_{2}\)O \(\rightarrow\) 4 OH\({}^{-}\). The areas with more Ti (Figure 7) showed a reduction in the presence of chlorine and a higher oxygen level caused by the formation of titanium oxide on the surface. The compound layer based on copper chlorides, titanium oxides and salts can act as a barrier against the corrosion process of Cu-Ti alloys in saline solutions, at least for a certain time. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Elements** & \multicolumn{2}{c}{**Cu\%**} & \multicolumn{2}{c}{**Cl\%**} & \multicolumn{2}{c}{**O\%**} & \multicolumn{2}{c}{**Ti\%**} & \multicolumn{2}{c}{**Na\%**} \\ \cline{2-11}
**Area** & **wt** & **at** & **wt** & **at** & **wt** & **at** & **wt** & **at** & **wt** & **at** \\ \hline Cast pct 1 & 40 & 21.3 & 29.3 & 28.2 & 16.1 & 34.3 & 7.7 & 5.5 & 7.2 & 10.8 \\ Cast pct 2 & 48.1 & 26.5 & 24.6 & 24.1 & 20.1 & 44 & 7.43 & 5.4 & - & - \\ Cast pct 3 & 47.8 & 26.2 & 23.2 & 22.7 & 20.7 & 45.1 & 8.35 & 6.1 & - & - \\ General cast & 42.6 & 22.4 & 25.8 & 24.4 & 22.3 & 46.6 & 9.4 & 6.5 & - & - \\ \hline Hot-rolled pct 1 & 42.3 & 23.1 & 26.4 & 25.8 & 17.8 & 38.6 & 10.1 & 7.3 & 3.5 & 5.2 \\ Hot-rolled pct 2 & 50.2 & 28.4 & 26.1 & 26.4 & 17.5 & 39.2 & 4.7 & 3.5 & 1.6 & 2.6 \\ Hot-rolled pct 3 & 56.3 & 36.6 & 32.4 & 37.8 & 9.4 & 21.6 & 1.5 & 1.3 & 1.5 & 2.7 \\ General hot-rolled & 49 & 27.5 & 26.6 & 26.7 & 17.3 & 38.6 & 4.8 & 3.6 & 2.3 & 3.5 \\ \hline EDS Error\% & 1.3 & & 0.9 & & 2.1 & & 0.3 & & 0.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical compositions obtained from the corroded surfaces of the experimental alloys over large areas and from selected points in Figure 6a,b. Figure 7: Main elements distributions identified on the surface of the rolled alloy after corrosion. The higher content of Na-based compounds in the rolled sample compared to the cast one, where they were identified only locally, may be related to the size of the compounds formed in the CuTi alloy.