Electrophoretic deposition of natural hydroxyapatite on medical grade 316L stainless steel

Natural hydroxyapatite has been electrophoretically deposited on medical grade 316L stainless steel. The suspension consisted of isopropyl alcohol and polyethylenimine. The substrates were 16 × 6 × 4 mm in dimension. Deposition was achieved on the cathode at 30, 60, and 90 V in 1 to 5 min at constant voltage. After deposition the samples were dried at room temperature for 24 h and deposition weight, roughness, and thickness of the coatings were measured. The coated samples were sintered in a vacuum furnace at 800 °C for 1 h. The surface morphology of the samples was studied by a scanning electron microscope, and phase purity of the coating material was investigated by XRD. The sample coated at 60 V and 3 min led to an adherent, continuous, and crack-free coating. The coating efficiency and thickness increased with increasing deposition time while the slope of the curves decreased which showed a decrease in deposition rate. Also, the current density decreased and yielded to saturation at the constant applied voltage during electrophoretic deposition. Quantitative analysis of the coatings after sintering showed some partial decomposition of natural hydroxyapatite to tricalcium phosphate. Additionally, the experimental results were also compared extensively with the theoretical proposed expressions.