In this work, we present a simple strategy of fabricating an N-doped graphene oxide coating on stainless steel for protective applications.

Application of biodegradable implants has received increasing attention for the treatment of bone damage due to their low adverse effects. To achieve better biocompatibility and enhanced corrosion resistance of biodegradable implants with improved wear resistance, multifunctional coatings need to be developed. Herein, a ceramic hybrid coating has been fabricated by a plasma electrolytic oxidation (PEO) technique using Ta₂O₅ nanoparticle inclusion on AZ31 Mg alloy in order to attain superior corrosion, wear behavior, and surface porosity that enable improved bioactivity. X-ray diffraction analysis of PEO coatings showed that the surface coating is mainly composed of Mg₃(PO₄)₂, MgO and Ta₂O₅ in different quantities based on PEO processing. Furthermore, scanning electron microscopy (SEM) analysis was employed to observe the surface of the resultant PEO hybrid coatings after and before wear tests. With Ta₂O₅ nanoparticles, PEO coatings showed excellent wear compared with pure PEO coatings. The efficiency of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements in simulated body fluid. Furthermore, in vitro cell culture studies were performed on MG-63 human cells to evaluate the biocompatibility of PEO coatings. A quantum chemical approach and force-field molecular dynamics simulation were employed to evaluate the interaction between the AZ31 Mg surface and PEO hybrid coatings. All of the observations evidently showed that the ceramic hybrid PEO coating provides improved wear and corrosion protection performance with superior biocompatibility with Ta₂O₅ nanoparticles, when compared to pure PEO coatings, due to its synergistic beneficial effect.

The bioactivity and the corrosion protection for a novel nano-grained Ti-20Nb-13Zr at % alloy were examined in a simulated body fluid (SBF). The effect of the SPS’s temperature on the corrosion performance was investigated. The phases and microstructural details of the developed alloy were analyzed by XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), and TEM (Transmission Electron Microscope). The electrochemical study was investigated using linear potentiodynamic polarization and electrochemical impedance spectroscopy in a SBF, and the bioactivity was examined by immersing the developed alloy in a SBF for 3, 7, and 14 days. The morphology of the depositions after immersion was examined using SEM. Alloy surface analysis after immersion in the SBF was characterized by XPS (X-ray Photoelectron Spectroscopy). The results of the bioactivity test in SBF revealed the growth of a hydroxyapatite layer on the surface of the alloy. The analysis of XPS showed the formation of protective oxides of TiO₂, Ti₂O₃, ZrO₂, Nb₂O₅, and a Ca₃(PO₄)₂ compound (precursor of hydroxyapatite) deposited on the alloy surface, indicating that the presented alloy can stimulate bone formation. The corrosion resistance increased by increasing the sintering temperature and the highest corrosion resistance was obtained at 1200 °C. The improved corrosion protection was found to be related to the alloy densification. The bioactivity and the corrosion resistance of the developed nanostructured alloy in a SBF renders the nanostructured Ti-20Nb-13Zr alloy a promising candidate as an implant material.