Novel synthesis of bioactive hydroxyapatite/f-multiwalled carbon nanotube composite coating on 316L SS implant for substantial corrosion resistance and antibacterial activity

We report on the synthesis of bioactive hydroxyapatite/multiwalled carbon nanotube composite coating on 316L SS implant by a spray pyrolysis technique. The samples were characterized for its structural and morphological properties using X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), and field emission scanning electron microscope (FE-SEM). The XRD results revealed an increased surface area and reduced crystallite size for HA/f-MWCNT composite coated 316L SS implant. The peak position in HA/f-MWCNT sample was slightly shifted, which could be attributed to the distortion by the substitution of functionalized carbon. SEM results show evenly grown spherical HA meso crystals uniformly distributed on the walls of f-MWCNTs. The presence of flower like nanoflake crystallites on the 316L SS implant surface beneficial for bioactivity. The vibrational spectral analysis confirmed the presence of OH groups centered at 3340 cm⁻¹ due to carboxyl functionalization of the MWCNTs. Compared to pure HA, the HA/f-MWCNT composite exhibited enhanced antibacterial activity with zone of inhibition of 12 mm against Escherichia coli. The HA/MWCNT composite films showed good corrosion resistance to the 316L SS implant. The corrosion resistance of the resultant coating was studied by the electrochemical analysis. The hybrid HA/f-MWCNT/SS composite exhibited higher corrosion resistance performance in stimulated body fluid with decreasing current density from 7.3 to 6.6 μΑ cm⁻² after MWCNT incorporation.