Evaluation of Corrosion Inhibition of Plasma Sprayed FsHA/YSZ Coating on β-Titanium (Ti-13Nb-13Zr) Alloy Using Electrochemical Techniques

α + β titanium alloys especially Ti-6Al-4V alloy have dominated implant industry over the years due to their high corrosion resistance, strength, and flexibility. However, their high modulus (110GPa) compared to the human bone (18-30GPa) results in aseptic loosening of implants. Hydroxyapatite (HA) coating on Ti-6Al-4V alloys has been used to mitigate these demerits, nevertheless, more still need to be done. Hence, the present study aims at developing a natural and economical bioceramic coating on low modulus Ti-13Nb-13Zr alloy substrates using plasma spraying technique for biomedical applications. The bioceramic used was natural HA derived from fish scales (FsHA) and FsHA doped yttria stabilized zirconia at (10-20 wt.%). FsHA/YSZ powders and the coated samples were examined by XRD and SEM/EDX and the surface roughness, microhardness and corrosion resistance of the uncoated substrate and coated samples determined. The XRD pattern showed good crystalline FsHA/YSZ powders for all the compositions while the microstructure of the coatings revealed a fine splat lamellar morphology with partially melted and non-melted FsHA particles along with evenly dispersed Zr particles within the coating matrix for the FsHA/YSZ coatings. The maximum surface roughness (4.215 µm) was found with the FsHA coating while FsHA/YSZ coatings presented the highest hardness values (492.5-536.9 Hv) compared to the FsHA coating (467.8 Hv) and the uncoated substrate (385.9 Hv). Similarly, the corrosion resistance of the Ti-13Nb-13Zr alloy was significantly improved with the deposition of FsHA/YSZ bioceramic coatings.