Hydroxyapatite coatings on Ti substrates by simultaneous precipitation and electrodeposition

This paper presents hydroxyapatite (HA) coatings electrodeposited onto titanium by a new electrochemical approach: one precursor is present in the electrolysis cell, while the other precursor is dropwisely added, simultaneously with the application of an electrochemical potential. The addition order of the precursors was alternated, and the Ti substrate surface modifications were evidenced using various characterization methods. The coatings displayed higher crystallinity, with HA crystals organized into hemispheres, and a double ceramic layer configuration: one uniform base layer (submicrometric crystals), continuous in all cases and with higher density, and one upper layer (micrometric units), uniform only for longer deposition times and with lower density. Adhesion tests were performed to determine coating-substrate bonding strength. Artificial saliva solution tests conducted at 37 degrees C for 30 and 60 days were followed by XRD and SEM characterizations. The coatings could be useful for dentistry or orthopaedics applications, favouring the implant connection with the living tissue.