Enhancing corrosion resistance of Ti6Al7Nb alloy using nano bioactive ceramic coating by EPD in biomedical applications

In this work, using the electrophoretic deposition (EPD) technique, Ti6Al7Nb alloy samples were coated with hydroxyapatite (HA) nanoparticles to enhance corrosion behavior and biological characteristics. In the absolute ethanol EPD suspension solution, hydroxyapatite concentrations varied at 2, 5, and 8 g/L, with chitosan as a binder. The EPD process potential was 40 V, the distance between the two electrodes was 1 cm, and the coating period was 4 min for all samples. X-ray diffraction (XRD). Scanning electron microscopy (SEM), and energy dispersive of X-ray (EDX) were used to test the coated sample. Corrosion behavior was also tested by measuring the open circuit potential (OCP) and polarization curve (Tafel). The wettability contact angle and adhesion tests were also measured. The optimum sample, coated with hydroxyapatite at 8 g/L, was immersed in simulated body fluid (SBF) for 1 month, and tested by XRD, SEM, and EDX. The results show that the corrosion rate was reduced 13 times, from 5.544 × 10−4 millimeters per year (mmpy) to 7.100 × 10−3 mmpy for the uncoated sample, and protection efficiency reached 92.19%. After immersion in SBF for 1 month, XRD and SEM results showed the appearance of a new hydroxyapatite layer with agglomerated particles, and the Ca/P ratio of 2.143 was close to the standard original ratio in the human body, an indicator for excellent osseointegration. The corrosion rate reached 2.841 × 10−4 mmpy, and the protection efficiency reached 96%, as an indicator of enhanced corrosion characteristics after immersion in SBF solution.