Preparation of hydroxyapatite coating on CoCrMo implant using an effective electrochemically-assisted deposition pretreatment

A hydroxyapatite (HA) coating is efficiently generated on CoCrMo implant alloys by employing an electrochemically-assisted deposition (ECAD) pretreatment followed by chemical immersion in a supersaturated calcification solution. CoCrMo was electrochemically treated in a calcium- and phosphate-containing solution for short time. A thin layer about 200 nm thicknesses, consisting mainly of amorphous calcium phosphate, was formed on the surface of the CoCrMo after the ECAD pretreatment. After the chemical immersion for 2 h, a layer of octacalcium phosphate was formed on the surfaces. A layer of HA was formed after 72 h immersion. The effectiveness of these treatments was demonstrated by comparison with the alkaline treated CoCrMo. Results showed that the ECAD pretreatment highly enhanced the capability of formation of HA on the CoCrMo surface, while only a small amount of CaP islands were formed on CoCrMo through traditional chemical treatment. A tensile test showed that the coating tightly bonded to the substrate. This work has explored an effective ECAD pretreatment to activate CoCrMo implant surface for generating HA coating.