Electrochimica Acta 55 (2010) 759–770 Contents lists available at ScienceDirect Electrochimica Acta j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e l e c t a c t a Electrochemical behavior of centrifuged cast and heat treated Ti–Cu alloys for medical applications Wislei R. Osório ∗ , Alessandra Cremasco, Protásio N. Andrade, Amauri Garcia, Rubens Caram Department of Materials Engineering, University of Campinas, UNICAMP, P.O. Box 6122, 13083 – 970 Campinas, SP, Brazil a r t i c l e i n f o Article history: Received 15 June 2009 Received in revised form 26 July 2009 Accepted 6 September 2009 Available online 13 September 2009 Keywords: Ti–Cu alloys Centrifuged casting Eutectoid microstructure EIS a b s t r a c t The aim of this study was to evaluate the general electrochemical corrosion resistance of Ti–5, 7.1 and 15 wt.% Cu alloys with a view to medical applications. A centrifuged casting set-up and a solution heat treatment at 900 ◦ C for 2 h were used to prepare the samples. Electrochemical impedance spectroscopy (EIS) and potentiodynamic anodic polarization techniques were used to analyze the corrosion resistance in a 0.15 M NaCl solution at 25 ◦ C. An equivalent circuit analyses was also conducted. It was found that the corrosion rate increased with increasing Cu content. The results have shown that the addition of Cu has not stabilized the ␤ phase. Martensite and Ti 2 Cu intermetallic particles provided by casting and heat treatment processes, respectively, have important roles on the resulting impedance parameters and passive current densities of the Ti–Cu alloys. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Due to their outstanding corrosion resistance as well as high specific strength, commercial application of Ti and Ti alloys is con- tinuously growing in the last few decades. Titanium is extensively applied in several markets including automotive,power genera- tion, marine and offshore, architecture,chemical, petrochemical, sport and medicine. Commercially pure Ti does not hold opti- mized mechanical behavior, which restricts its use in a number of fields, especially when high mechanical strength is necessary. Nevertheless,its mechanical behavior may be notably enhanced by alloying titanium with a number of other elements. Addition of alloying elements allows one to manipulate the balance of stable and metastable phases in the final microstructure and hence, tita- nium alloy mechanical properties, including mechanical strength, ductility and elastic modulus. In dentistry, titanium alloys are applied in the manufacture of a number of dental devices such as bridges and partial denture frame- works [1–4]. When in use, these devices are frequently subjected to relatively high mechanical stresses.Consequently,in order to reduce elastic deformation, they must be manufactured with mate- rials having a high modulus of elasticity. On the other hand, the most utilized route in the making of dental devices is the preci- sion casting process. Casting of Ti alloys is not a simple task as it always comprises several complexities,including high melting temperature, affinity with interstitial elements and considerable ∗ Corresponding author. Tel.: +55 19 3521 3320; fax: +55 19 3289 3722. E-mail address: wislei@fem.unicamp.br (W.R. Osório). activity with mould materials. An alternative method employed to minimize these difficulties as well as to improve the mechanical behavior of c.p. Ti (commercially pure Ti) is to make use of copper as an alloying element. Ti alloyed with Cu is reported to provide adequate biocompati- bility [5], reasonable corrosion resistance [4,6] and comparatively lower melting temperature [4,7,8], which greatly favors cast- ing procedures. Since the 1950s,a number of studies have been focused on the Ti–Cu alloys for industrial applications. Results from those investigations show that Ti–Cu alloys may present very high mechanical strength associated with good formability [4]. In the last 20 years, dental titanium casting technology has made considerable progress.Kikuchi et al. [4] have shown that centrifuged cast Ti–Cu alloys permits yield strengths as high as 650 MPa to be attained, a value which is considerable higher than that of c.p.Ti and of most of the dental casting Co–Cr alloys.Sun et al. [9] showed that the application of a solution heat treatment has strengthened Ti–2.5%Cu alloy due to the formation of Ti 2 Cu intermetallic particles after ␤ phase decomposition into ␣-Ti and Ti 2 Cu. One of the most inconvenient aspects in terms of biomate- rials applications is the degradation caused by corrosion, which occurs due to the material interaction with body physiological flu- ids [10–12]. As a result, the corrosion resistance can be considered a fundamental characteristic of biomaterial components and it is associated with ions release of metallic species, which can be harm- ful for the organism. Degradation generally occurs on the surface of Ti-based components due to the chemical and electrochemical reactions between titania and ions in the surrounding media. In this context, electrochemical studies are very useful to establish 0013-4686/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2009.09.016