## 3 Results
### Corrosion Resistance  
Figure 4 illustrates the Tafel polarization curves of the nitridded 316L stainless steel samples subjected to varying levels of deformation. The self-corrosion potential and the calculated self-corrosion current density are summarized in Table 3. The tests for corrosion resistance were carried out in a 3.5% NaCl solution. Table 3 illustrates that the matrix and the deformation of the nitridded specimens exhibit a significant disparity in self-corrosion current density results, differing by nearly an order of magnitude. This variation can be attributed to the corrosion resistance of stainless steel, which is primarily influenced by the matrix's chromium content that facilitates the formation of a dense chromium oxide protective layer on the surface. During nitriding treatment at 500 \({}^{\circ}\)C, nitrogen atoms dissolve within the austenite grains, leading to their precipitation from the supersaturated austenite phase. This process results in the formation of chromium nitride through the interaction of chromium present in the matrix. The precipitation of nitrides in the nitriding layer causes the diffusion of chromium from the matrix to the surface layer, consequently diminishing the corrosion resistance. Therefore, the corrosion resistance of the nitridded specimen is reduced in comparison to that of the non-nitrided substrate. As depicted in Figure 4 and Table 3, the self-corrosion potentials of the nitrided samples with different deformation levels are comparable to those of the original samples; however, the self-corrosion current densities are generally elevated. This increase is due to the fact that, following deformation, the precipitation temperature of the chromium-rich second phases ranges from 400 to 850 \({}^{\circ}\)C, with their primary precipitate being the chromium carbide M\({}_{23}\)C\({}_{6}\)[14]. During the nitriding process at 500 \({}^{\circ}\)C, similar compounds may form, resulting in potential differences with the CrN compounds generated during nitriding and at defect sites. Moreover, the depletion of chromium in localized areas leads to the \"chromium-poor phenomenon\" [15], which significantly elevates the current density during the electrochemical corrosion process and markedly diminishes pitting corrosion resistance [16]. The nitriding process, when conducted at temperatures exceeding 450 \({}^{\circ}\)C [17], leads to the dissolution of nitrogen atoms within the austenite grains. This nitrogen can readily precipitate from the supersaturated austenite phase and subsequently react with chromium present in the matrix to form chromium nitride. This precipitation preferentially occurs along grain boundaries, resulting in a reduction in chromium content in the surface layer of the matrix. Consequently, this phenomenon, referred to as the \"chromium-poor phenomenon\", adversely affects the material's corrosion resistance. Furthermore, after undergoing compression deformation at room temperature, 316L stainless steel exhibits a substantial number of shear bands, stacking faults, and other defects. These imperfections compromise the uniformity and chemical stability of the chromium-rich oxide film on the stainless steel's surface. The presence of martensite can also induce the localized activation and dissolution of the oxide film, further impairing its corrosion resistance. In conclusion, an increase in deformation levels correlates with a decline in the corrosion resistance of the nitrided samples. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Ecorr/V** & **icorr/A.cm\({}^{-2}\)** \\ \hline Substrate & \(-0.303\) & \(8.913\times 10^{-7}\) \\
0 & \(-0.25\) & \(5.687\times 10^{-6}\) \\
10\% & \(-0.25\) & \(8.769\times 10^{-6}\) \\
20\% & \(-0.272\) & \(8.18\times 10^{-7}\) \\
30\% & \(-0.289\) & \(9.183\times 10^{-7}\) \\
40\% & \(-0.271\) & \(2.164\times 10^{-6}\) \\
50\% & \(-0.261\) & \(1.1007\times 10^{-6}\) \\ \hline \hline \end{tabular}
\end{table}