## 3 Results and Discussion
The composition of the resulting secondary phases suggests that these phases acted as microanodes. The results of microanalysis in the destroyed grain boundary (Point 3) indicate significant chromium depletion in comparison to the bulk of the material, thus confirming the conclusion about selective dissolution of chromium-enriched secondary phases, i.e., microanodes, upon the contact with molten salt. It should also be noted that the total sum of the elements determined in the crack zone (i.e., point 3 in Figure 12) was below 100%. This was caused by the mounting resin penetrating  
Figure 10: Corrosion resistance of individual metals in molten FLiNaK (650 \({}^{\circ}\)C, 100 h). \begin{table} \begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multicolumn{2}{c}{**Grain (Point 1)**} & \multicolumn{2}{c}{**Excess Phase (Point 2)**} & \multicolumn{2}{c}{**Crack Zone (Point 3)**} \\ \cline{2-7}  & **wt. \%** & **at. \%** & **wt. \%** & **at. \%** & **wt. \%** & **wt. \%** & **at. \%** \\ \hline Al & 0.2 & 0.5 & 0.3 & 0.7 & 0.1 & 0.2 \\ Cr & 32.9 & 36.6 & 45.1 & 49.6 & 11.3 & 11.8 \\ Fe & 0.6 & 0.6 & 0.4 & 0.4 & 1.9 & 1.8 \\ Ni & 58.3 & 57.6 & 44.6 & 43.6 & 65.2 & 60.4 \\ Mo & 8.0 & 4.8 & 9.6 & 5.7 & 10.1 & 5.8 \\ \hline \hline \end{tabular}   
Similar observations were made for the VDM® Alloy 59 and KhN62M-VI alloys (Tables 7 and 8, Figures 13 and 14). Excess phases (Point 2) were significantly enriched in chromium, and localization of corrosion processes along the grain boundaries was observed for all samples (Figures 5 and 6). The composition of the secondary phases indicates that these phases acted as microanodes. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multicolumn{2}{c}{**Grain (Point 1)**} & \multicolumn{2}{c}{**Excess Phase (Point 2)**} & \multicolumn{2}{c}{**Crack Zone (Point 3)**} \\ \cline{2-7}  & **wt. \%** & **at. \%** & **wt. \%** & **at. \%** & **wt. \%** & **at. \%** \\ \hline Al & 0.2 & 0.6 & — & — & — & — \\ Cr & 23.2 & 26.7 & 36.8 & 43.0 & 3.8 & 4.6 \\ Fe & 0.5 & 0.4 & 0.5 & 0.6 & 4.8 & 5.4 \\ Ni & 63.6 & 64.8 & 42.5 & 43.7 & 73.1 & 79.2 \\ Mo & 12.5 & 7.5 & 20.2 & 12.7 & 13.1 & 8.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Results of X-ray microanalysis of points 1, 2, and 3 of the KhN62M-VI alloy sample after corrosion in molten fluoride systems. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multicolumn{2}{c}{**Grain (Point 1)**} & \multicolumn{2}{c}{**Excess Phase (Point 2)**} & \multicolumn{2}{c}{**Crack Zone (Point 3)**} \\ \cline{2-7}  & **wt. \%** & **at. \%** & **wt. \%** & **at. \%** & **wt. \%** & **at. \%** \\ \hline Al & 0.2 & 0.5 & 0.3 & 0.7 & 0.1 & 0.2 \\ Cr & 32.9 & 36.6 & 45.1 & 49.6 & 11.3 & 11.8 \\ Fe & 0.6 & 0.6 & 0.4 & 0.4 & 1.9 & 1.8 \\ Ni & 58.3 & 57.6 & 44.6 & 43.6 & 65.2 & 60.4 \\ Mo & 8.0 & 4.8 & 9.6 & 5.7 & 10.1 & 5.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of X-ray microanalysis at points 1, 2, and 3 of the Hastelloy® G-3® alloy sample after corrosion in molten fluoride systems. Figure 14: Regions of X-ray microanalysis of the microstructure of the KhN62M-VI alloy after corrosion in FLiNaK + UF\({}_{4}\) at 750 \({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multicolumn{2}{c}{**Grain (Point 1)**} & \multicolumn{2}{c}{**Excess Phase (Point 2)**} & \multicolumn{2}{c}{**Crack Zone (Point 3)**} \\ \cline{2-7}  & **wt. \%** & **at. \%** & **wt. \%** & **at. \%** & **wt. \%** & **at. \%** \\ \hline Al & 0.4 & 0.9 & 0.2 & 0.5 & – & – \\ Cr & 1.5 & 1.9 & 1.2 & 1.6 & – & – \\ Mn & 0.9 & 1.1 & 0.7 & 0.9 & – & – \\ Fe & 1.2 & 1.4 & 0.9 & 1.1 & 1.8 & 1.4 \\ Ni & 68.7 & 76.6 & 41.7 & 60.2 & 62.3 & 46.4 \\ Mo & 27.3 & 18.1 & 55.3 & 35.7 & 15.4 & 7.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Results of X-ray microanalysis of points 1, 2, and 3 of the Hastelloy® B-3®alloy sample after corrosion in molten fluoride systems.