Leila Fathyunes - Assistant professor, Department of Materials Science and Engineering, University of Bonab, ۵۵۵۱۷۶۱۱۶۷,Bonab, Iran
Seyed Omid Reza Sheykholeslami - Faculty of Materials Engineering, Research Center for Advanced Materials, Sahand University of Technology, ۵۱۳۳۵۱۱۹۹۶, Tabriz, Iran
Vida khalili - Assistant professor, Department of Materials Science and Engineering, University of Bonab, ۵۵۵۱۷۶۱۱۶۷, Bonab, Iran

Despite having the superior mechanical properties, NiTi alloy could not meet all clinical requirementsfor implants. The bio-inert surface of this alloy is one of the reasons for failing its implantation.Releasing the high amount of harmful nickel ions from NiTi alloy is another serious concern causingallergic problems such as inflammation and cells death. Therefore, the surface modification of this alloyis necessary for improving its performance in the biomedical applications. In this work, the surfacemodification of NiTi was carried out by pretreatment and applying the bioactive calcium phosphatecoating. For pretreatment of NiTi alloy, we used two different processes of alkaline treatment in 5 MNaOH solution at 60 °C for 24 hour and heat treatment at 500 ˚C for 30 minute. Moreover, a bioactivecoating of calcium phosphate was applied by pulsed current electrochemical deposition at a constantcurrent density of 15 mA/cm2 and duty cycle of 0.1 on the pretreated surface of NiTi. The results showedthat heat treatment further decreased the nickel release from NiTi into Ringer's solution as compared tothe alkaline treatment. Moreover, wettability of the NiTi sample pretreated with these two processeswas different that affected the microstructure of the top calcium phosphate coating. In fact, the highersurface tension resulted from increasing the wettability caused the formation of porosities with largersize in the microstructure of the coating applied by electrochemical deposition method.

NiTi, alkaline treatment, heat treatment, calcium phosphate coating, electrochemical deposition, nickel release, microstructure