## 4 Conclusions  
A corroded layer covering an un-corroded body makes the assessment of the stress state more difficult (when compared with the components being un-corroded). MBN is sensitive against the rolling direction of low-alloyed steel, the degree of corrosion attack, and the direction of measurements with respect to the direction of the exerted stress as well as the amplitude of the stress. Synergistic contributions of these aspects do not enable distinguishing among them when only the MBN value is employed. MBN values for all investigated low-alloyed steels are not exclusive for any mixture of the aforementioned aspects, and they overlap with respect to the variable stress state, corrosion attack, and/or the direction in which the MBN measurement occurs. For this reason, monitoring components with respect to their corrosion damage and superimposing stress should be based on a mixture of MBN parameters extracted from the raw MBN signals. This can be summarized as follows:  
- Higher MBN values are linked with lower thicknesses of a corroded layer;  
- Higher MBN values are linked with higher tensile stresses in RD and a lower MBN in TD;  
- _PP_ values in RD are higher for heavily corroded samples, but the sensitivity against stress is limited;  
- _FWHM_ values in RD are higher for heavily corroded samples, but the sensitivity against stress for MC700 and MC1100 is also limited;  
- _FWHM_ for S235 drops down with tensile stress in RD;  
- _PP_ and _FWHM_ in TD exhibit a lack of sensitivity against corrosion attack as well as tensile stress. Finally, it should be considered that the multi-parametric approach would be beneficial in the proposal of a suitable concept when all sensitive MBN parameters, such as MBN, _PP_, and _FWHM_, are employed. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **MBN—Effective Value** & _PP_ & & **FWHM** \\ \cline{2-6}  & **RD** & **TD** & **RD** & **TD** & **RD** & **TD** \\ \hline corrosion & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\uparrow\) & \(\uparrow\) & \(\uparrow\) \\ \hline Tensile stress & \(\uparrow\) & \(\downarrow\) & \(\uparrow\) & \(\uparrow\) & \(\downarrow\)\({}^{*}\) & \(\downarrow\)\({}^{*}\) \\ \hline \hline \end{tabular} \(\uparrow\)—ascending evolution; \(\downarrow\)—descending evolution; \({}^{*}\)—flat evolution of MC1100.  
\end{table} 
Table 2: Evolution of MBN parameters as a function of corrosion damage and the superimposing tensile elastic stresses. **Author Contributions:** Conceptualization, M.N. and F.B. ; methodology, F.P. and T.K. ; software, R.K. and T.K. ; validation, F.B. ; formal analysis, R.K.; investigation, M.N., F.P., R.K. and F.B. ; resources, F.B. and T.K. ; data curation, R.K. and F.P., writing--original draft preparation, M.N. and F.P. ; writing--review and editing, M.N. ; visualization, R.K. and T.K. ; supervision, F.P. and F.B. ; project administration, F.B. ; funding acquisition, F.B. All authors have read and agreed to the published version of the manuscript. **Funding:** This publication was realized with support from the Operational Program Integrated Infrastructure 2014-2020 of the project: Innovative Solutions for Propulsion, Power and Safety Components of Transport Vehicles, code ITMS 313011V334, co-financed by the European Regional Development Fund. Additionally, support of the VEGA project 1/0052/22 is also gratefully acknowledged. This research was also funded by Operational Program Integrated Infrastructure: Application of innovative technologies focused on the interaction of engineering constructions of transport infrastructure and the geological environment, ITMS2014+ code 313011 BWS1. The project was co-funded by the European Regional Development Fund. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** The raw data required to reproduce these findings cannot be shared easily, due to technical limitations (some files are too large).