**4. Conclusions**

Mo plays an important role as an alloying element by increasing the strength and toughness of maraging steel. Moreover, the tendency to form retained austenite increases along with increasing Mo concentrations. In the present study, we found that in both 3.5% NaCl solution and 1 M H2SO4 solution, the generated maraging steel exhibited improvements in corrosion resistance according to increasing Mo content up to 4.6%. However, corrosion resistance decreased at 9.8% Mo due to increased embrittlement in the alloy. These results were confirmed by the Nyquist plots, showing the same trends in corrosion behavior. Furthermore, Raman spectroscopy verified decreases in the corrosion rate due to the presence of higher fractions of corrosion products ( α-FeOOH) in the M9.8 (9.8% Mo) sample.

**Author Contributions:** Conceptualization, A.H.S., H.H., and M.S.S.; data curation, A.H.S., H.H., and M.S.S.; formal analysis, A.H.S., H.H., and M.S.S.; funding acquisition, M.S.S.; investigation, A.H.S. and M.S.S.; methodology, A.H.S., H.H., and M.S.S.; resources, H.H.; supervision, A.H.S., H.H., and M.S.S.; writing—original draft, A.H.S., H.H., and M.S.S.; writing—review and editing, A.H.S., H.H., and M.S.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This project was supported by the NSTIP Strategic Technologies Program, gran<sup>t</sup> number (12-ADV2465-02), Kingdom of Saudi Arabia.

**Data Availability Statement:** The experimental datasets obtained from this research work and then the analysed results during the current study are available from the corresponding author on reasonable request.

**Acknowledgments:** This project was supported by the NSTIP Strategic Technologies Program, gran<sup>t</sup> number (12-ADV2465-02), Kingdom of Saudi Arabia.

**Conflicts of Interest:** The authors declare no conflict of interest.
