Synthesis of biphasic calcium phosphate (BCP) coatings on β‒type titanium alloys reinforced with rutile-TiO2 compounds: adhesion resistance and in-vitro corrosion

In this study, β type Ti‒29Nb‒13Ta‒4.6Zr alloys coated with biphasic calcium phosphate (BCP) reinforced with rutile-TiO 2 compounds by sol-gel technique to evaluate its possible usage in biomaterial science. Calcium nitrate tetrahydrate (Ca(NO 3 ) 2 ∙4H 2 O), di-ammonium hydrogen phosphate (NH 4 ) 2 HPO 4 ), ammonium hydroxide (NH 4 OH), and titanium (IV) propoxide (Ti(OC 3 H 7 ) 4 ) (Merck, Germany) were used as precursors for producing the BCP-only and BCP/TiO 2 composite coatings. Synthesis and coating procedure, surface morphology, adhesion strength, and corrosion results of the coated samples have been investigated in details. XRD technique has been used in order to characterization of BCP phases. The morphological observations of coatings were determined by using a scanning electron microscopy (SEM). In-vitro corrosion behaviors of the coatings have been determined with polarization method in Ringer’s electrolyte at body temperature. It was found that the BCP/TiO 2 coating synthesized on TNTZ alloy has higher scratch resistance than BCP-only coating due to its containing rutile-TiO 2 compounds. In addition, it can be said that the BCP/TiO 2 coated sample was less susceptibility to corrosion than the BCP-only coatings and uncoated TNTZ sample in simulated body fluid. Highlights A new method has been proposed for production of biphasic calcium phosphate (BCP). The phase has been coated on the β type Ti‒29 Nb‒13Ta‒4.6Zr (TNTZ) alloys by sol-gel. The coating has higher adhesion resistance if the BCP phase contains TiO 2 compounds. In-vitro resistances of the coatings were found higher than uncoated TNTZ alloy.