Electrochemical behavior of different structural states of the alloy Ti 60 Ni 40 Shubhra Mathur a, ⁎, Rishi Vyas a , Rohit Jain b , Praveen Kumar c , K. Sachdev a , S.K. Sharma a a Department of Physics, Malaviya National Institute of Technology, Jaipur-302017, India b Department of Physics, Jagannath Gupta Institute of Engineering and Technology, Jaipur-303905, India c Surface Physics and Nanostructure Group, National Physical Laboratory, New Delhi-110012, India abstract article info Article history: Received 10 February 2011 Received in revised form 24 April 2011 Available online 27 May 2011 Keywords: Corrosion; Polarization; X-ray photoelectron spectra Potentiodynamic polarization studies were carried out on nanocrystalline I, nanocrystalline II and nanocrystalline III states having crystallite size 35 ± 5 nm, 18 ± 2 nm and 10 ± 2 nm of the alloy Ti 60 Ni 40 in 1MH 2 SO 4 aqueous medium. It was observed that the nanocrystalline III state exhibits superior corrosion resistance as compared to the nanocrystalline II and nanocrystalline I states of the alloy Ti 60 Ni 40 . XPS studies were also performed after corrosion test and it was observed that nanocrystalline III state contains only Ti 2+ and Ti 4+ species whereas nanocrystalline I and nanocrystalline II state contains Ti 2+ , Ti 3+ and Ti 4+ along with some unoxidized metallic Ti 0 in the case of nanocrystalline I state. Thus the small crystallite size and the presence of only Ti 2+ and Ti 4+ species in the form of TiO and TiO 2 leads to the formation of a protective oxide film which is adherent, stable and improves the corrosion resistance of the nanocrystalline III state of the alloy Ti 60 Ni 40 . © 2011 Elsevier B.V. All rights reserved. 1. Introduction Metallic glasses have received considerable technological and scientific interest because of their excellent mechanical, magnetic and chemical properties [1]. They require a rapid cooling rate of 10 5 – 10 6 K/s whereas bulk metallic glasses can be produced at low cooling rates of 1–100 K/s [2]. Interest in nanocrystalline materials has focused the attention of researchers worldwide in elucidating the role of nanocrystals in changing the properties of glassy alloys [3]. In fact, much earlier a new type of soft magnetic materials were developed by utilizing a nanocrystalline structure formed by anneal- ing the amorphous Fe-based alloys at low temperatures [4]. Koester et al. reported that a nano phase was formed in the Zr–Al–Ni–Cu based metallic glasses with a wide supercooled liquid region and high glass forming ability [5]. Kapaklis et al. studied the thermal and structural properties of Pd 40 Cu 30 Ni 10 P 20 alloy and it was reported that the introduction of nanocrystalline precipitation in the amorphous matrix enhances the elastic properties [6]. In another investigation Pardo et al. observed that nanocrystalline phase has better corrosion resistance than the amorphous phase, which was attributed to the possible medium range ordered region in the amorphous phase, which are expected to initiate localized pitting leading to greater corrosion than nanocrystalline phase [7,8]. Hence the nanocrystalline state in amorphous matrix shows remarkable change in the properties of amorphous alloys [6–16]. The improvement in the properties of amorphous alloys due to the presence of nanocrystalline state in amorphous matrix increases its practical applications [17–20]. Thus an electrochemical study is very important for understanding their environmental degradation and for determining their suitability for possible applications. This motivated us to carry out the present study on comparison of the electrochem- ical behavior of different structural states of the alloy Ti 60 Ni 40 in 1 M H 2 SO 4 aqueous medium. 2. Experimental The Ti 60 Ni 40 was obtained in the ribbon form (10 cm × 1 cm × 30 μm) by melt-spinning technique. The nanocrystalline specimens were obtained after removing 5–6 μm and 9–10 μm from the air side surface by polishing. The X-ray diffraction pattern of different structural states of the alloy Ti 60 Ni 40 was recorded at 300 K using FeK α radiation on a Philips make X-ray diffractometer PW 1840 and phases was identified by PCDFWIN data. Potentiodynamic polarization studies were carried out using potentiostat Echo-chemi (AutoLab-30) in 1M H 2 SO 4 aqueous medium under identical experimental conditions. The details on the experimental procedure followed can be found in another paper [21,22]. Weight loss studies were also carried out in order to confirm the polarization results. The specimens were immersed in the solution for about 720 h. The corrosion rate is then calculated from the measured weight loss data [23].The polarization and weight loss results were obtained under identical experimental conditions in several experimental runs with a deviation of about ±10%. Journal of Non-Crystalline Solids 357 (2011) 3084–3087 ⁎ Corresponding author. Tel.: + 91 141 2713215. E-mail address: shubhramathur3@gmail.com (S. Mathur). 0022-3093/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2011.04.016 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol