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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.

The aim of this paper was to investigate the formation of an amorphous phase in the coating structure due to reduction in porosity and improvement in corrosion resistance of Ti6Al4V alloy during PEO process. The effect of crystallization on the electrochemical corrosion behavior and surface property of Ti6Al4V coating fabricated by plasma electrolytic oxidation (PEO) technique, was investigated in 5 wt %HCl solution. The coating compositions and electrochemical behaviors were examined by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) and polarization tests. The results showed that an increase in the ionic strength of electrolyte had a direct effect on the crystal size, the lattice strain and corrosion resistance. An increase in lattice strain due to Ti–O–Si led to a reduction in coating adhesion and corrosion resistance. A significant effect in phase transformation for Titania in the PEO process was not only led to an increase in polarization resistance but also reduced the number and size of porosity.