Murilo Oliveira Alves Ferreira

This work aims to investigate the effects of chloride ion-rich environment on the global corrosion behaviour of the IN718 alloy fabricated using the Directed Energy Deposition (DED) by open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS) in 0.6 mol L-1 NaCl solution, comparing it to the conventional IN718 alloy. The results demonstrated that the DED method could produce corrosion resistance responses that are at least equivalent (top), and potentially superior (transversal and longitudinal), to those of the traditional IN718. Such findings underscore the effectiveness of the process in replicating, and possibly enhancing, the corrosion resistance properties of the IN718/DED alloy.

This investigation examined the efficacy of Nb₂O₅-based coatings, deposited by using the reactive sputtering technique, on the corrosion and corrosion-fatigue behaviour of 2198-T8 aluminium alloy used as aircraft material. Global corrosion behaviour was accessed by Open Circuit Potential (OCP), Potentiodynamic Polarization curves (PPc) and Electrochemical Impedance Spectroscopy (EIS) techniques in 0.6 mol L⁻ ¹ NaCl solution. Fatigue crack growth (FCG) tests were conducted under controlled loading conditions in both air and saline environments. Comprehensive structural and morphological characterisations were performed using advanced microscopy and spectroscopy techniques, including Atomic Force Microscopy (AFM), Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDX), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and Electron Backscatter Diffraction (EBSD). The results unequivocally demonstrated the protective nature of the coating, significantly enhancing the alloy's durability as evidenced by corrosion and fatigue-corrosion tests. These findings underscore the substantial potential of Nb₂O₅ coatings in extending the service life of 2198-T8 aluminium alloy when subjected to aggressive environments, thereby providing invaluable data for aerospace engineering applications. Graphical abstract

To enhance interaction with the host tissue and protect the metal surface, various surface treatments can be applied to dental implants. This study aimed to produce layer-by-layer (LbL) films by alternated immersion of the titanium sample into polyacrylic acid (PAA) and chitosan solutions, obtaining a PAA/chitosan bilayer architecture, seeking to improve the corrosion resistance. For this purpose, 03 experimental groups (n = 05) were performed: Ti-Cp (as control), Ti-Cp+8 bilayers PAA/chitosan, and Ti-Cp+12 bilayers PAA/chitosan. The corrosion behavior was assessed by using open-circuit potential (OCP), potentiodynamic polarization curves (PPcs) and electrochemical impedance spectroscopy (EIS) techniques, conducted in 0.9 wt% NaCl solution at a controlled temperature of 25 ± 1 °C. The samples were characterized morphologically and structurally by atomic force microscope (AFM), scanning electron microscopy/energy-dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD) techniques before and after the corrosion tests. The electrochemical results significantly highlight the beneficial influence of coatings based on PAA/chitosan in enhancing the corrosion resistance of titanium. These findings not only corroborate the feasibility of using alternative materials for the protection of titanium but also open new possibilities for the development of innovative coatings that can be applied within the biomedical sector, serving as mediators for medicinal purposes, particularly in osteoconductive interventions.

This research investigates the influence of Nb₂O₅ coatings, produced by using reactive sputtering technique, on the surface of middle-tension specimens M(T), regarding fatigue crack growth curves (da/dN versus ΔK) under exposure to a 0.6 mol L^–1 NaCl saline solution. Results demonstrated the corrosion process occurred in the vicinity of the crack tip, where stresses are elevated, and significant plastic deformation prevails, notably influenced by slip bands that induce microcracks, exposing fresh material layers to the corrosive surroundings. The Nb₂O₅ coatings enhanced the fatigue-corrosion resistance of the 2198-T851 aluminium alloy. This study marks an initial step towards more comprehensive investigations into the impact of Nb₂O₅ coating on improving the mechanical properties of the 2198-T851 aluminium alloy.

The Ti-6Al-4V alloy is widely used in orthopedic and dental implants due to its excellent mechanical, corrosion, and biological properties. However, it exhibits several limitations that can compromise its performance in clinical applications. Notably, the alloy suffers from a high coefficient of friction, which can lead to increased wear and reduced longevity of implants under relative movement conditions. Additionally, Ti-6Al-4V shows susceptibility to localized corrosion in physiological environments, particularly in the presence of bodily fluids that may result in the formation of pitting. These challenges underscore the need for surface modifications that can enhance the alloy’s tribological performance, thereby improving its overall efficacy and durability as a biomaterial in medical settings. In this context, the manuscript presents applied and innovative research that assesses the impact of implementing nanostructured Nb₂O₅ coatings through the reactive sputtering technique on the wear performance of Ti-6Al-4V alloy under both air and artificial saliva (AS) solution conditions using a Pin-on-Disk apparatus. The nanostructured Nb₂O₅ coating demonstrated the ability to reduce the wear rate and volume by up to 88% without inducing any modifications to the R_a and R_t of Ti-6Al-4V, a feature that is desirable for applications in implantable devices. The reduction in wear can be attributed to the shift from adhesive wear mechanisms on uncoated surfaces to abrasive mechanisms on coated surfaces. This research highlights the strategic advantage of utilizing Brazil’s abundant niobium resources to advance biomaterial technology and facilitate applications that benefit public health.

The nanosecond pulsed fibre laser (NsPFL) treatment is extensively employed to distinguish hospital surgical instruments (micro-surgical forceps, surgical blades, orthopaedic drills, and high-precision laparoscopic tools), which are generally composed of stainless steel. Nevertheless, if the laser parameters are not properly optimised, this process may unintentionally provoke corrosion. Maintaining the structural integrity of these materials is essential for ensuring patient safety and minimising long-term costs. This work aims to optimise the laser scanning parameters for marking 316L stainless steel (316L SS), seeking to improve its corrosion resistance. The corrosion behaviour was assessed by using open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS) techniques, conducted in 0.9% wt NaCl solution at a controlled temperature of 25 ± 1 °C. A comprehensive study employing optical profilometry has significantly enhanced our understanding of the corrosion micromechanisms of 316L SS, comparing specimens both with and without NsPFL treatment. Considering applications involving environments rich in chloride ions, the results indicated that the NsPFL-316L SS samples demonstrated markedly enhanced performance compared to the untreated base material after 48 h of immersion in 0.9% wt NaCl solution. This improvement is particularly noteworthy given the widespread utilisation of 316L SS in the manufacturing of surgical instruments, where corrosion resistance is of paramount importance.

Niobium-based oxides have garnered increased attention in recent years for their remarkable enhancement of corrosion resistance, as well as biofunctional properties of various metallic materials, including 316L SS. However, the mechanical properties of these promising coatings have not been fully elucidated. This study investigated how much the environmental conditions (air, artificial saliva, and NaCl solution) impact the wear performance of 316L SS without and with Nb₂O₅ coatings deposited via the reactive sputtering technique. The results exhibited a notable decrease in friction coefficient (55% in air, 18% in artificial saliva, 10% in 0.9 wt% NaCl solution), wear area (46% in air, 36% in AS, 17.5% in 0.9 wt% NaCl solution), and wear rate (44.0% in air, 19.5% in AS, 12.0% in 0.9 wt% NaCl solution). Ultimately, the results obtained in the present study elucidate the synergistic mechanisms of corrosion and wear in 316L SS containing Nb₂O₅ coatings, highlighting its significant potential for applications in the biomedical sector.