## 4 Results and Discussion
### Electrochemical Impedance Spectroscopy Measurements
#### 4.1.2 Mixture with Lithium Content (LiNaK)NO\({}_{3}\) Testing
This is due to the fact that the corrosion process of the different thermal plants, the use of nickel-based alloys such as HR-224 will increase the final cost of materials and it is necessary to test new materials. In this case, the evolution of the need for new ferritic steels that possess excellent properties, such as resistance to corrosion, has led to the development of a high-temperature material called VM12, which has a chrome content of 12% and is of industrial interest in different high-temperature applications (>550 \({}^{\circ}\)C) [26; 27; 28]. Corrosion resistance and electrochemical analysis of ferritic steel VM12 has not been reported in different investigations in molten salts, specifically in the ternary mixture with lithium content proposed in this article. According to [PERSON] et al. [29], the potential of the material VM12 as belonging to the family of ferritic steels compared to austenitic steels or nickel-based alloys reflects a significant price variation, and seems to have a possible use in future solar power concentration plants. For this reason, two tests were carried out at different times, as shown in Figures 14 and 15, at 100 and 1000 h respectively of immersion in the ternary mixture. The tests at 100 and 1000 h presented behavior in the protective layer equivalent model circuit; like the previous materials, they are represented in Tables 9 and 10. Ferritic steel VM12 showed excellent properties with respect to corrosion in contact with the lithium nitrate ternary mixture. Analyzing the different molten salt corrosion models using electrochemical impedance spectroscopy, specifically the protective layer model, it was easier to understand how the different metal/molten-salt system interfaces interact in the first hours of contact due to the high temperature corrosion process. At the same time, concepts of interaction between the molten salt and the layers of the metal interfaces related to ion diffusion and charge transfer processes through the different electrical components that are used by this test (EIS) were explained. In this way, the oxides that are formed in the different layers of the metal are strongly linked to the evolution of the high and low frequency impedance spectra of the tests on the proposed materials. The lack of a conceptual methodology for the corrosion process in molten salts to find different parameters, such as the thickness of the boundary layer, means that the EIS method, together with the corrosion mechanisms, allow us to understand the importance of its combination to use them more adequately in industrial applications. Complementing this, [PERSON] et al. [10] shows us objectively that the deposition of the different layers formed in the study steels due to the ion diffusion processes, fundamentally in the first hours of contact with the metal, contributes to the need to monitor these stages and analyze the evolution of the corrosion process in molten salts. The oxidation caused by the effects of the high temperature in different materials of solar thermal storage generates the formation of different compounds, many of which can be inferred of certain form on the basis of the mechanisms of corrosion in nitrates; we can find more stable compounds along the process, as well as, the effect of lithium mainly (as a result of LiNO\({}_{3}\)) and the other alkaline ions in the corrosion, due to the formation of other unstable compounds like iron and lithium oxides (LiFeO\({}_{2}\), LiFe\({}_{5}\)O\({}_{8}\) and others). Apart from the oxides known as the (FeCr)\({}_{3}\)O\({}_{4}\) which form the inner layer of the protective layer and Fe\({}_{2}\)O\({}_{3}\) as the outer layer of the metal, it is possible that  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Time** & \(R_{s}\) & \(C_{all}\) & \(\beta_{all}\)  
LiFeO\({}_{2}\) can form an individual layer, which in a way functions as a corrosion inhibitor.