The aim of this work was to investigate the nanomechanical, adhesion and corrosion resistance of hydroxyapatite (HAP) coatings. The electrodeposition process was used to elaborate the HAP coatings on Ti₆Al₄V alloy. The effect of hydrogen peroxide concentration H₂O₂ on the electrolyte and the heat treatment was studied. Surface morphology of HAP coatings was assessed, before and after heat treatment, by scanning electron microscopy associated with X-ray microanalysis (SEM-EDXS). Moreover, X-ray diffraction (XRD) was performed to identify the coatings’ phases and composition. Nanoindentation and scratch tests were performed for nanomechanical and adhesion behavior analysis. The corrosion resistance of the uncoated, the as-deposited, and the heat-treated coatings was investigated by electrochemical test. The obtained results revealed that, with 9% of H₂O₂ and after heat treatment, the HAP film exhibited a compact and homogeneous microstructure. The film also showed a crystal growth: stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). After heat treatment, the nanomechanical properties (H, E) were increased from 117 ± 7 MPa and 24 ± 1 GPa to 171 ± 10 MPa and 38 ± 1.5 GPa respectively. Critical loads (L_C1, L_C2, and L_C3) were increased from 0.78 ± 0.04, 1.6 ± 0.01, and 4 ± 0.23 N to 1.45 ± 0.08, 2.46 ± 0.14, and 4.35 ± 0.25 N (respectively). Furthermore, the adhesion strength increased from 8 to 13 MPa after heat treatment. The HAP heat-treated samples showed higher corrosion resistance (R_p = 65.85 kΩ/cm²; I_corr = 0.63 µA/cm²; E_corr = −167 mV/ECS) compared to as-deposited and uncoated samples.

Titanium oxides and their alloys are widely used in medical applications because of their biocompatibility. However, they are characterized by their low resistance to corrosion. The HaP + TiO₂ nanocomposites’ coating was applied in different experiments, especially on a Ti-6Al-4V substrate with the spray pyrolysis process to deal with such weakness. The TiO₂ content effects on the surface morphology and the phase composition were investigated using a scanning electron microscopy, X-ray microanalysis (SEM-EDXS) and X-ray diffraction (XRD). The mechanical properties were determined with nanoindentation. The potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and simulated body fluid (SBF) solution environment tests were carried out to investigate the corrosion resistance of HaP + TiO₂/Ti6Al4V systems. The experimental findings revealed that sprayed thin films possessed uniform morphology. The coatings’ nanoindentations proved that the HaP + 20% TiO₂ coating hardness (252.77 MPa) and the elastic modulus (52.48 GPa) overtopped those of the pure hydroxyapatite coatings. The corrosion test demonstrated that the corrosion current density of about 36.1 µA cm⁻² and the corrosion potential of the order of −392.7 mV of HaP + 20% TiO₂ was lower compared to the pure HaP coating.