Accelerating the formation of a calcium phosphate layer on NiTi alloy by chemical treatments

A chemical treatment procedure was used to treat the acid–alkali treated NiTi samples. The accelerated formation of a dense and uniform calcium phosphate layer in simulated body fluid on the chemically treated NiTi alloy was observed within two days of immersion. The proposed chemical treatment procedure resulted in enhanced adsorption of Ca2+ and HPO42- ions onto the treated surface and consequent local Ca2+ and HPO42- ions supersaturation. The thickness of the adsorption layer, composed mainly of Ca2+ and HPO42- ions, was about 100 nm.