## 5 Conclusions  
Summarising all the previous findings, it becomes clear that the statistical analysis proved the expected fact that the technological process of production of NiTi alloys affects their favourable characteristics significantly from the point of view of reducing the susceptibility to the corrosion process. Analysis of linear models of the corrosive behaviour of the two observed NiTiol alloys shows significant differences in the corrosive behaviour of these alloys. Namely, the linear models suggest the following facts:  
* NiTi-1 alloy corrodes significantly faster in conditions of exposure to the sea;
* NiTi-1 alloy shows similar corrosive behaviour under the influence of air and tide;
* The corrosive characteristics of the NiTi-2 alloy differ significantly when samples come out affected by different marine environments;
* In all marine environments, the NiTi-2 alloy behaved completely differently from the NiTi-1 alloy. The corrosive behaviours of both NiTiol alloys are very complex, and cannot be characterised with Normal distribution or with two-parameter continuous distributions. Consequently, in the process of fitting distributions, it is necessary to consider three-parameter continuous distributions, that can describe the empirical data adequately. The Kolmogorov-Smirnov goodness-of-fit test revealed the following continuous distributions as the best ranked three-parameter distributions for the three observed seawater environments:  
* NiTi-1, air influence, three-parameter Log-Logistic distribution;
* NiTi-2, air influence, Burr distribution;
* NiTi-1, tide influence, Burr distribution;
* NiTi-2, tide influence, three-parameter Log-Logistic distribution;
* NiTi-1, sea influence, Generalised Extreme Value distribution;
* NiTi-2, sea influence, General Pareto distribution. A comparative analysis of the behaviour of two NiTiol alloys shows the following characteristics of their corrosive processes:  
* Statistically significant differences were observed when samples were exposed to air or tide;
* The largest differences in the depth of corrosive changes in NiTiol alloys occurred in samples exposed to the effects of the tides;
* The NiTi-1 alloy showed a tendency of reduced corrosive processes in relation to the values of corrosion depth in the NiTi-2 alloy in all three observed seawater environments. However, although the three-parameter theoretical distributions proved to be adequate for modelling the corrosion process in the observed alloys in all three environments, nonlinearities were detected, especially in the tails of the fitted distributions. Therefore, it is necessary to focus future research on the analysis of nonlinear models that will take into account the stochastic side of the corrosion process. To conduct an analysis of this type, it is necessary to form bigger databases with even more extensive empirical samples, which would allow increasing the statistical significance of the findings. In this study,only FIB analyses were performed on a NiTi-1 alloy (disk surface) and NiTi-2 alloy (on a flat bar surface). Using additional complementary methods, such as X-ray fluorescence analysis, auger electron spectroscopy, X-ray mapping or X-ray photoelectron spectroscopy, further conclusions can be drawn with high reliability about the actual changes of the alloy under the influence of different seawater environments, as well as their comparison regarding quality. Conceptualisation, N.K. and S.I. ; methodology, N.K. and S.I. ; software, N.K. ; validation, N.K., S.I., G.V. ([PERSON]), G.V. ([PERSON]) and R.R. ; formal analysis, N.K. and S.I. ; investigation, N.K., S.I. and G.V. ([PERSON]); resources, S.I., G.V. ([PERSON]) and R.R. ; data curation, S.I. and R.R. ; writing--original draft preparation, N.K. and S.I. ; writing--review and editing, N.K., S.I., G.V. ([PERSON]) and R.R. ; visualisation, N.K. and S.I. ; supervision, G.V ([PERSON]), G.V. ([PERSON]) and R.R. ; project administration, S.I. ; funding acquisition, S.I. All authors have read and agreed to the published version of the manuscript.