## 2 Materials and Methods
### FIB Corrosion Depth Measurement Data Analysis
Even in the case of the NiTi-2 alloy, the values of the corrosive influence of air are small, while the values of the depth of corrosion created under the influence of the sea are the highest. However, the NiTi-2 alloy shows significant differences compared to the NiTi-1 alloy when the tidal corrosion depth \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Alloy/Environment/Time** & **6** & **12** & **18** & **Total** \\ \hline \multirow{3}{*}{NiTi-1} & air & 15 & 10 & 30 & 55 \\  & tide & 20 & 20 & 26 & 66 \\  & sea & 15 & 37 & 25 & 77 \\ \hline \multirow{3}{*}{NiTi-2} & air & 22 & 20 & 40 & 82 \\  & tide & 25 & 22 & 32 & 79 \\  & sea & 24 & 22 & 29 & 75 \\ \hline \multirow{3}{*}{} & Total & 121 & 131 & 182 & 434 \\ \cline{1-1} \cline{2-6}  & & & & & \\ \end{tabular}
\end{table} 
Table 4: The number of measurements performed on each alloy in different seawater environments after 6, 12 and 18 months of exposure. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{6}{c}{**NiTi-2 Chemical composition**} \\ \hline
**Spectrum** & **In stats.** & **O** & **Ti** & **Ni** & **Total** \\ \hline Spectrum 1 & Yes & 4.55 & 37.08 & 58.37 & 100.00 \\ Spectrum 2 & Yes & 4.81 & 37.26 & 57.94 & 100.00 \\ Spectrum 3 & Yes & & 46.03 & 53.97 & 100.00 \\ Spectrum 4 & Yes & & 44.47 & 55.53 & 100.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical composition of the NiTi-2 corrosion layers identified by EDS analysis. is observed. The values of corrosion depth in the NiTi-2 alloy become similar to the values of depth of corrosion created in the sea. These values increase significantly compared to the values created under the influence of air, and have much greater variability. Figure 4: Presentation of corresponding FIB measuring locations: (**a**) NiTi-1, (**b**) NiTi-2; Micro-view of an FIB cut: (**c**) NiTi-1, (**d**) NiTi-2; Corrosion depth values after 1 year in the sea measured by FIB: (**e**) NiTi-1, (**f**) NiTi-2; Presentation the places where the EDS analyses were performed: (**g**) NiTi-1, (**h**) NiTi-2. Table 5 shows the basic descriptive statistics of the measured values of the corrosion depth caused by air, tides and sea, after 6, 12 and 18 months. In the first 18 months of the experiment, the NiTi-1 alloy had small values of the depth of corrosion created under the influence of air and tide. Notably higher values of corrosion wear of NiTi-1 alloys are shown after 12 months of exposure to the sea. After 12 months of sea influence, the mean value of corrosion wear of 316.39 nm was measured with a Standard Deviation of 200.88 nm, while after 18 months these values were 476.17 nm and 151.33 nm, respectively. In the case of the NiTi-2 alloy, significant corrosion processes occurred after 6 months of exposure to the sea and after 12 months of tides. Under the influence of the sea, after 6, 12 and 18 months of exposure, the mean values of corrosion depth were 144.27 nm, 239.28 nm and 548.02 nm, respectively, with corresponding Standard Deviations of 73.66 nm, 97.55 nm, 227.56 nm, respectively. The NiTi-2 alloy had mean values of measured corrosion depth of 158.02 nm and 286.59 nm, respectively, formed under the influence of the tide after 12 and 18 months. The Standard Deviation of 116.09 nm and 190.89 nm of the measured depth of corrosion caused by the tide was observed in these time intervals. Figure 5: Display of raw data for the NiTi-1 alloy. Figure 6: Display of raw data for the NiTi-2 alloy.