Development of thin-film hydroxyapatite coatings with an intermediate shellac layer produced by dip-coating process on Ti6Al4V implant materials

A thin layer of hydroxyapatite (HAp) coating has been developed on Ti6Al4V substrates using a dip-coating process. An intermediate layer of shellac (natural resin) was applied in between the substrate and the coating film to improve the adhesion strength without the need for any secondary annealing process. The adhesion strength was measured as 7.14 MPa. The surface of the developed coating was characterized using a scanning electron microscope. The total coating thickness was found to be 30 microns, and the surface roughness parameters were measured as 0.93 μm (Ra), 1.17 μm (Rq), and 6.67 μm (Rz). The dip-coated samples were also subjected to dissolution behavior study and in vitro study. The measured parameters of the coating suggest the use of this method as an alternative to other expensive and temperature-dependent coating methods for producing HAp coating with better adhesion strength.