Based on their high mechanical strength, Ti-based high-entropy alloys (HEAs) are of great potential as materials for high-performance reduced-diameter dental implants. Despite previous studies demonstrating their corrosion resistance in various simulated body fluids, their resistance in simulated buccal conditions has yet to be confirmed. In this work, the corrosion behavior of two Ti-based HEAs, TiZrHfNb, and TiZrHfNbTa was evaluated in comparison to CP-Ti and Ti-6Al-4V in artificial saliva (AS) solution and in AS with fluoride ion content (ASF). A set of electrochemical tests (electrochemical impedance spectroscopy, cyclic polarization, and Mott–Schottky) was employed and complemented with surface characterization analyses (scanning electron microscopy and atomic force microscopy) to determine dissolution and passivation mechanisms of the alloys. In general, the HEAs exhibited a far superior corrosion resistance compared to CP-Ti and Ti-6Al-4V alloys in both solutions. In the AS solution, the TiZrHfNb exhibited the highest polarization resistance and pitting potential, indicating a high corrosion resistance due to the formation of a robust passive layer. Whilst in the ASF solution, the TiZrHfNbTa showed a greater corrosion resistance due to the synergistic effect of Nb and Ta oxides that enhanced passive film stability. This finding emphasizes the role of Ta in elevating the corrosion resistance of Ti-based HEAs in the presence of fluoride ions and confirms the importance of chemical composition optimization in the development of next-generation dental alloys. Based on its electrochemical corrosion behavior, TiZrHfNbTa HEAs are promising new materials for high-performance reduced-diameter dental implants.

This study investigates the corrosion inhibition efficiency of [2-(thiophen-2-yl)-1-(thiophen-2-ylmethyl)-1H-benzo[d]imidazole] and its Zn and Cu complexes for mild steel in 1.0 M HCl. The ligand was selected for its non-toxic profile and high electron density, favoring strong adsorption onto the metal surface. Electrochemical methods, including EIS, PDP, LPR, and CASP, were employed to evaluate the inhibitors’ performance. The results showed a significant decrease in corrosion current density and increased polarization resistance, with the Zn complex achieving the highest inhibition efficiency (93.8%). EIS fitting confirmed the formation of a protective film with high charge transfer and film resistance. Surface analyses by SEM and EDS revealed smoother steel morphology and inhibitor adsorption. XPS confirmed the presence of Fe³⁺, Zn²⁺and Cu²⁺ oxides, as well as all active inhibitor elements on the surface, supporting a mixed inhibition mechanism. The enhanced performance of the metal complexes is attributed to synergistic effects between the metal ions and the heterocyclic ligand, offering a promising strategy for the design of effective and environmentally friendly corrosion inhibitors.

This study provides a detailed assessment of the corrosion-inhibiting performance of a previously synthesized pyrazole derivative (R9) for mild steel, using both experimental and theoretical methods. Electrochemical measurements, including potentiodynamic polarization and electrochemical impedance spectroscopy, showed that R9 achieved a maximum inhibition efficiency of 81% at a concentration of 10⁻³ M in 1 M hydrochloric acid. This improvement was reflected in the marked decrease in corrosion current density from 604 to 94 µA·cm⁻². The inhibitor displayed mixed-type behavior, influencing both anodic and cathodic corrosion reactions. This was confirmed by the small shift in corrosion potential recorded with and without R9, along with the increase in polarization resistance and the enhanced protection of the steel surface. Inductively coupled plasma spectrometry was used to measure dissolved metal ions, while scanning electron microscopy combined with energy-dispersive X-ray spectroscopy confirmed the formation of an adsorbed protective film on the steel surface. These findings further supported the effectiveness of R9 and agreed well with the electrochemical results. In the theoretical part, quantum chemical calculations on the isolated inhibitor R9 and the Fe-R9 complex (density functional theory, molecular electrostatic potential, Fukui indices, and atomic charges) were coupled with molecular simulations based on both molecular dynamics and Monte Carlo methods to provide a comprehensive understanding of the corrosion inhibition mechanism. The findings from the electronic structure studies, active site predictions, and adsorption analyses demonstrated effective and stable complexation of the R9 molecule with the steel. The results revealed an excellent correlation between the experimental and theoretical methods employed, highlighting the significance and robustness of the present study.