Computer assisted corrosion analysis of hydroxyapatite coated CoCrMo biomedical alloys M. İbrahim Coşkun a,b , İsmail Hakkı Karahan c , Teresa D. Golden b, ⁎ a Department of Physics, Faculty of Arts and Sciences, Kilis 7 Aralık University, Kilis 79000, Turkey b Department of Chemistry, University of North Texas, 1155 Union Circle #305070, Denton, TX 76203, USA c Department of Physics, Faculty of Arts and Sciences, Mustafa Kemal University, Hatay 31040, Turkey abstract article info Article history: Received 27 March 2015 Revised 22 May 2015 Accepted in revised form 24 May 2015 Available online 29 May 2015 Keywords: CoCrMo alloys Electrodeposited films Hydroxyapatite EIS IR spectroscopy Zview and COMSOL modeling programs Corrosion studies Bio-metallic CoCrMo alloys were coated with hydroxyapatite layers by electrodeposition to improve biocompat- ibility. Surface morphology was analyzed by scanning electron microscopy. Chemical composition was investi- gated by FTIR. In vitro corrosion performance was examined by electrochemical impedance spectroscopy and Tafel measurements in a simulated body fluid. Corrosion performance of the coatings deposited at various pH values was investigated using Zview and COMSOL computer modeling programs. Both programs successfully modeled EIS results. Increasing the electrolyte pH improved corrosion performance of the biocompatible coat- ings. Electrolyte pH influenced corrosion properties, chemical composition, and surface morphology of the coatings. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Bio-metallic implant materials such as stainless steel, titanium al- loys, and CoCrMo alloys are widely used in dental applications and sur- gical operations as load-bearing implant materials due to the superior mechanical properties and extremely high corrosion resistance [1]. However, it is reported that metallic biomaterials do not bond sponta- neously to human bone and need mechanical locking [2,3]. CoCrMo based metallic biomaterials have poor biocompatibility and are encap- sulated into the body by fibrous tissue that isolates them from the sur- rounding bone [4]. Therefore, in recent years, research has focused on improving biological performance of metallic implants. One way to overcome this handicap for metallic implants is coating with a bioactive layer like calcium phosphate (CaP) [2]. It has been reported that coating CoCrMo alloys with a CaP bioactive layer improves biocompatibility by providing a better bone-bonding ability [4]. One CaP compound, hydroxyapatite, is a more stable phase in biological conditions and hydroxyapatite coated CoCr implants could bond directly to human bone [3]. The porous structure of hydroxyapatite layer improves osseointegration by providing spaces for bone ingrowths, and the bond between metallic implant and human bone becomes much stronger [5]. Recent studies showed an improvement in bone contact on hydroxyapatite coated implants compared to uncoated CoCr [6]. In recent years, the usage of CoCrMo alloys in the medical industry has been increasing as an alternative to titanium alloys due to better mechanical properties especially higher surface strength which results in higher corrosion resistance [6]. It is essential to apply effective methods for coating and characterization of Ti and its alloys to include CoCr-based alloys [7]. However, there are limited studies reported about electrodeposition of hydroxyapatite on CoCrMo biomaterials [7]. Therefore, more investigation is still necessary to understand the effect of electrodeposition parameters on in vitro corrosion behavior of the hydroxyapatite coated CoCrMo alloys. Many coating methods such as plasma spray, sol–gel, electrophoret- ic, RF sputtering and electrodeposition can be used for coating hydroxy- apatite on the surface of metallic implants [8]. Among these methods plasma spray is the only clinically accepted method [8]. The disadvan- tages of the plasma spray method such as extremely high temperature of operation, difficulty of microstructure control and modification, have directed researchers to develop new methods [9]. Among all the coating methods, electrodeposition is favored because of the ability to coat complex geometries, comparably low operation temperature, and control of coating composition [10–12]. Due to these advantages, we used an electrodeposition method to coat hydroxyapatite layers onto CoCrMo bio-metallic implants. Surface & Coatings Technology 275 (2015) e1–e9 ⁎ Corresponding author. E-mail address: tgolden@unt.edu (T.D. Golden). http://dx.doi.org/10.1016/j.surfcoat.2015.05.037 0257-8972/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat