Effect of Cl^– and ${\text{NO}}_{3}^{ - }$ Ions on Microstructure and Properties of TiO₂–CeO₂ Nanostructured Composite Coatings Obtained Through Plasma Electrolytic Oxidation (PEO) on Ti6Al4V

Abstract—

Rare earth cerium oxide synthesized from cerium (III) chloride and cerium (III) nitrate salts in electrolytes were used to develop nanostructured composite coatings by plasma electrolytic oxidation (PEO) technique on Ti6Al4V. The micro-hardness (542 HV) and corrosion resistance of fabricated coat in the electrolyte containing cerium (III) nitrate was notable. Formation of the ceria/titania nanostructured composite originated from the nitrate salt during PEO process acted as a barrier to the porosity growth and exhibited a higher impedance resistance (8.6 × 10⁵ Ω Cm²) at the lower frequency and higher corrosion resistance (2.26 × 10^–3 mm y^–1) in 0.1 M HCl solution at the room temperature than the fabricated coat in PEO-electrolyte containing the cerium (III) chloride salt. Structural characterization techniques such as (X-ray diffraction) XRD, (scanning electron microscope) SEM and (energy disperse spectroscopy) EDS were used to investigate the microstructure and morphology of the coatings. Fourier transform infrared spectroscopy (FT-IR) was utilized to recognize and to confirm the development of bonds with wavelength of 457 and 530 cm^–1 corresponded to the stretching vibration (Ce–O) of the attracted cerium oxide nanoparticles in the coatings. The result demonstrated that CeO₂ nanoparticles were created and drawn into the discharge channels of sample CS3 during the PEO has led to the enhancing of the composite coating thickness (31 µm) and corrosion resistance, too.